Sunday, 4 December 2022

Leaf-Eating Monkeys: Leading by a Nose

Proboscis monkey (male)
Perhaps the most distinctive and well-known of all the colobine monkeys is the proboscis monkey (Nasalis larvatus). Sufficiently distinctive that it's hard to confuse it with anything else, it was first described as a species all the way back in 1787 by botanist Friedrich von Wurmb, then working for the Dutch East India Company, and given its own genus in 1812.

Indeed, it is strange enough that, during the 20th century, it was assumed to represent a very early side-branch in colobine evolution, existing outside all the other groups in the subfamily. That wasn't just because of its odd appearance, but also because it had two extra pairs of chromosomes to every other colobine monkey. But it turns out that that's a false signal and that, not only are proboscis monkeys a relatively recent branch within the subfamily, their closest relatives include the snub-nosed monkeys whose noses are noted for being extraordinarily short.

Saturday, 26 November 2022

Miocene (Pt 36): Dawn of the Seals

Allodesmus
In this series so far, I have covered the mammalian wildlife of the Miocene continent by continent, showing how the diversity of animals then was just as great as it is now. But there is a group of mammals that a time traveller to the period would have been able to observe along the coasts of those continents - especially during their breeding season - that I have not yet mentioned.

Today, the seals are divided into two subfamilies (I have reviewed all living species of seal here): the phocine or "northern" seals, which live in the Northern Hemisphere, and the monachine or "southern" seals, which are primarily found in the Southern Hemisphere, but do include three living species in the north. 

Sunday, 20 November 2022

The Importance of Blue Bullshit

Monkeys and apes in general, and humans in particular, have a relatively poor sense of smell but the same is far from true of most other mammal species. For such animals, scent can be an important method of communication and this is often done through scent-marking, leaving long-term messages that can be understood by other passing members of your species.

A common way to do this is by rubbing specially adapted scent glands onto objects - these glands are often on the feet or the sides of face, which is why many animals will rub their heads against things to mark their territory. An alternative is to either urinate or defecate in a particular location, the natural aroma of the excreta often being aided by anal scent glands. We are all familiar with a dog's need to mark its territory in this way and it's hardly alone in this respect.

This can provide all sorts of useful information to other animals from the same species, such as territorial ownership, social dominance, willingness to mate, and so forth. When the method used to deposit this information is defecation rather than urinating, the result is termed a latrine or midden - which, in the biological sense, are basically alternative words for "dungheap". Animals that use this method of scent-marking include rhinoceroses, lemurs, and antelopes. (And we can but wonder what human cities would be like had we evolved from a species that communicated in this way).

Sunday, 13 November 2022

Plague and the Prairie Dogs

Populations of animals are not always stable from year to year, even ignoring the effects of direct human activity or climate change. If there is a prolonged drought, plants may die off, reducing the population of herbivores, which, in turn, reduces the number of predators that feed on them. This much is part of the natural cycle of life and death.

Perhaps the most famous example, sufficiently so to turn up in some school textbooks, is the case of the Canada lynx. This eats almost nothing but showshoe hares, so when the supply of the hares runs low, the lynx are more likely to be malnourished, so that mothers give birth to smaller litters. This means that there are fewer lynx around, which leads to the snowshoe hare booming, which means more food for the lynx, so they have larger litters, their population increases, they eat the hares so that the hare population goes down... and so on. Because the effect works through the litter size of the lynx, which take time to reach maturity, the lynx population rises and falls about a year behind that of the hares, and the entire cycle takes a decade or so to come full circle. We have records of this going back to the early 19th century from the fur-trappers of the Hudson Bay Company, and it doubtless goes back well into prehistory.

This is not the only example but it shows how such things can be perfectly natural. But that's not always the case; sometimes human activity can destabilise animal populations, leading to boom and bust cycles, without actually endangering them and driving them to extinction - although it may, of course, make such a thing more likely. For a couple of examples outside the world of mammals, we can look to the way that wild salmon populations fluctuate due to parasite loads, which they probably picked up from farmed salmon, or the way that pollution and overfishing lead to a boom-bust cycle in starfish and sea urchin populations.

For a more mammalian example, we can turn to the prairie dog.

Prairie dogs (Cynomys spp.) are a type of burrowing ground squirrel, most closely related to the marmots - and only much more distantly to the gophers, which are not squirrels and are also physically quite a bit smaller. There are five species of prairie dog, one of which is found only in northern Mexico, with the other four found across the Great Plains of the US. Of these four, one lives from southern Utah and Colorado down to New Mexico and Arizona, one lives immediately north of that, just about crossing the southern border of Montana, and a third is an endangered species restricted to only one small area in Utah between the first two. 

The remaining species is the most widespread. This is the black-tailed prairie dog (Cynomys ludovicianus) and it is generally found further to the east than the other three American species, although there is considerable overlap in the middle. The Rio Grande forms an effective barrier to the species in Texas, but they do cross over the border just south of eastern Arizona and are found in a broad band northward from there all the way to Montana and North Dakota, with the very northern extent of their range just across the Canadian border in Saskatchewan.

Prior to the arrival of Europeans, black-tailed prairie dogs (and presumably the other species) are thought to have been present in high numbers across their range, occupying wide stretches of the landscape. It's harder to tell how common they were during the 18th and 19th centuries, since they weren't the sort of thing that people in the area tended to make more than passing mention of and there certainly weren't detailed surveys. But, absent much in the way of human interference across that part of the continent at the time, it seems likely that they were still common, and had stable populations.

That changed in the early 20th century.

In 1901, the US Department of Agriculture published a calculation that suggested the animals ate so much forage that eradicating them would allow an additional 1,500,000 cattle to be reared in Texas alone. It's likely that Texan farmers didn't need this encouragement to try and get rid of the perceived pests, but in 1916, the federal government stepped in and started sponsoring official campaigns to poison and kill off the animals. The program continued, under various guises, until it was stopped by presidential order in 1972 but poisoning prairie dogs remains perfectly legal for individual ranchers.

This, it has to be said, has in no way led to any existential threat to the species' survival (and the endangered Utah species is protected by law). There are thought to be around 18 million black-tailed prairie dogs across the US today and, while their population may have declined in some areas, overall it's likely held fairly steady over the last few decades. Over shorter timescales, though, it undergoes a dramatic boom and bust cycle. 

And it isn't the poisoning campaigns that are doing it.

Instead, the main reason that the population declines so dramatically at the start of the 20th century, and continues to fluctuate wildly today is the introduction of a foreign disease to which the prairie dogs (and American animals in general) had no natural immunity. That disease is the plague.

Yes, the actual disease that caused the Black Death. It isn't called "bubonic plague" or any of the other human-related terms when rodents catch it and is instead called "sylvatic plague". But it's caused by exactly the same bacterium (Yersinia pestis) and is, like the human version, transmitted through flea bites - although, in the case of prairie dogs it's likely that other routes of transmission, such as infected carcasses or breathing in droplets breathed out by other small mammals, may be at least as, if not more, important. 

Whatever the precise details, colonies of black-tailed prairie dogs are regularly hit by outbreaks of plague, causing rapid population crashes that only slowly recover. The time between outbreaks seems to vary between five and fifteen years, sufficiently common to restructure and reduce the prairie dog populations. Even between outbreaks, a low level of plague seems to persist in the population, perhaps forming a reservoir from which the next one will arise.

Understanding this is important for a couple of reasons. For one thing, ranchers are probably not wrong when they say that high populations of prairie dogs cause problems for them; they really do reduce the available forage for cattle (or sheep) although this may affect the cattle less than one might think. 

From a conservation point of view, however, it's significant that black-tailed prairie dogs are a "keystone species", one whose existence is disproportionately important to maintaining an entire ecosystem. Indirectly, the presence of prairie dogs reshapes the grasslands in ways that are beneficial to burrowing owls, mountain plovers, and pronghorn, among others. More directly, they provide an important food source for many local predators, most notably various species of hawk. If they keep dying off, clearly this is going to be an issue.

One area in which this has been studied is the Thunder Basin National Grassland in northeastern Wyoming. For 21 years, between 1997 and 2018, scientists mapped the extent and number of black-tailed prairie dog burrows across the area as waves of the plague came and went. During this time period, there were three local outbreaks of plague. A major outbreak in 2002 almost wiped out the local animals, which had only partially recovered when a second wave hit in 2005. This was smaller, affecting primarily the colonies in the southwestern corner of the study area, but continued for a full three years before petering out. A long slow, rebuilding followed so that, by 2017, prairie dog colonies covered more of the land than they had before the first outbreak; the following year, the third wave hit and wiped almost all of them out again.

The fact that the second outbreak was on a different scale than the other two, and the changes in colony size over the intervening years means that it's not simply a matter of population density reaching some critical value before the plague starts to spread again. This makes it difficult to predict when waves of the plague will hit, or how long it will take for the prairie dogs to recover. But one pattern that was observed, and which supported previous findings, related to the weather. 

During dry years, the prairie dogs cannot feed on food as lush and nutritious as they might like, and consequently end up underfed, unfit, and susceptible to disease. Under normal circumstances, they can recover from that, but if the following year is unusually hot and damp, fleas spread and an outbreak becomes more likely. So the conditions in a single year might not have much effect, but two of the right sort in succession create a problem.

Perhaps more significantly, the study also showed that the periodic crashes in population and loss of entire colonies meant that just 8% of the study area was inhabited by the animals for over seven years at a time. The seven-year cut-off was chosen because previous work had shown that that is roughly how long it takes for prairie dogs to have a longlasting effect on the local plantlife and to fulfil their role as a keystone species. So, in other words, despite the animals being present, in over 90% of the area studied they kept dying out before their efforts could really bear fruit. It's also likely that, even in the very best years, immediately before a crash, the population never reached the heights it had in the 19th century before the plague reached the Americas from Asia.

That which does not kill you does not always make you stronger.

[Photo by "Musicaline" from Wikimedia Commons.]

Sunday, 6 November 2022

Leaf-Eating Monkeys: Monkeys on the Mountainsides

Golden snub-nosed monkey
Much of eastern China is dominated by two great river basins: the Yellow River in the north and the Yangtze in the south. In the western parts of the country, the upper reaches of the two basins are separated by the Qinling Mountains, running eastward from the vast Tibetan Plateau. And here, in addition to many other unique animals and plants, we find a rather strange species of monkey.

This is the golden snub-nosed monkey (Rhinopithecus roxellana) and its oddity merely begins with its unusual appearance. As the name implies, its fur is mostly golden, ranging from a brownish-red hue to a much brighter golden-yellow. Contrasting stripes of black fur run down the outer edges of the limbs and there are white patches on the back of the thighs. All of these colour patterns are brighter in the males, which are also noticeably larger than the females, indicating that these are likely used in sexual signalling - something supported by the fact that the genitalia also have a contrasting dark colour.

Sunday, 30 October 2022

Horns v. Geography - Relationships Among Rhino Species

White rhino
Rhinoceroses are amongst the largest land animals alive today, exceeded in size only by the elephants. As one might imagine, given their distinctive appearance, the group has a long evolutionary history. What is perhaps less obvious is that the family was once much larger than it is today, with many species living side-by-side. In total, we have so far named something like 100 species of fossil rhinoceros and, while some of those will probably not survive more detailed analysis, it's also true that there must be several we haven't found yet. Either way, it's quite a lot.

Most of these lived during the Miocene epoch (although the family is older than this) with the number of species thinning out during the following, Pliocene, epoch between around 5 and 2 million years ago. Even so, we know of nine species that lived during the later Ice Ages. Four of these, however, did not survive their end, leaving us with the five that - in some cases only just - survive today.

Sunday, 23 October 2022

The Lion Stalks Tonight

In the jungle, the mighty jungle, the lion probably does not sleep tonight.

The main reason for this is that lions don't really live in the jungle. Their primary habitat is savannah and open grasslands and while they can be found found in dry woodland (especially in India) they aren't found in the tropical rainforests that we typically associate with the word "jungle". Indeed, a map of Africa showing where you can find lions would have a very noticeable gap in the middle where the Congo jungle is - along, of course, with blank spaces over the harsher deserts. The idea of lions living in dense jungle probably owes more to Tarzan than reality.

Sunday, 16 October 2022

Decline of the Woodrats

The wild mice and rats of the Americas are not members of the true "mouse family", the Muridae, but instead belong to the Cricetidae, a name which translates as "hamster family". The vast majority of species in the family are not, however, hamsters, since the group includes both the voles (of which there are many) and the aforementioned New World mice and rats. Many of these latter are found in South America, with plenty more in Mexico and Central America. Most of them are mouse-sized, an example of the great success of the mouse body-plan where, despite having diverged from the true mice over 30 million years ago, such creatures as the American deer-mice differ from the house mouse by, at best, having a different colour pattern.

Just as some members of the mouse family developed larger size, evolving into such things as the familiar sewer rat (which, of course, has been introduced to America, even though it's not native there) so to did some of their New World counterparts. In the southern US, three different lineages of such creatures can be found: the muskrat (which is actually a giant vole), the cotton rats (which are related to the vast collection of South American rats and mice), and a third group variously called pack rats or woodrats.

Sunday, 9 October 2022

Leaf-Eating Monkeys: The Colourful Doucs of Vietnam

Red-shanked douc

Modern genetic analysis has shown that the leaf-eating monkeys of the Old World consist of three, related, evolutionary branches. Two of these, the colobus monkeys of Africa, and the langurs of Asia, had long been recognised as distinct, but the third was not always so. The monkeys belonging to this branch had, for the most part, previously been considered to be langurs, or at least part of the langur line, but it turns out that they split off from the others early on. Because of the comparative recency of this discovery, this third group doesn't have any distinctive common name and nobody seems to have come up with a scientific one, either. ("Rhinopithecinini" would seem the obvious choice to me, but one can see why nobody bothered).

So, instead, this group, when scientists need to refer to it, ends up being called the "odd-nosed monkeys". Even then, not all of them have noses that look (at least to me) especially odd, and this is most clearly true of the doucs. 

Saturday, 1 October 2022

Miocene (Pt 35): Crash Bandicoot and the Giant Platypus

Nimbacinus
When we think of marsupials, the animal that's probably most likely to come to mind first is the kangaroo, likely followed by the koala. Both of these animals, along with wombats and possums, belong to the largest order of marsupials, technically referred to as the diprotodonts - a term that literally means "two front teeth" on account of the enlarged, vaguely rodent-like incisors that characterise the family. These are used to clip at vegetation, since the group is overwhelmingly herbivorous.

This was less true in the Miocene, and that's because of the existence of marsupial lions. Or, more accurately, of thylacoleonids, members of the "marsupial lion" family, since the truly lion-sized animal best known by that name didn't live until much later. The group originated towards the end of the previous epoch, when some herbivorous, probably wombat-like, animal switched to a more meaty diet, its front teeth becoming blade-like in order to cut into flesh. They seem to have prospered during the Miocene, with three different genera currently recognised.

Sunday, 25 September 2022

Ain't No Mountain High Enough

Almost anywhere you can go on Earth, you will find life. A field of molten lava might be going a bit far, but otherwise, life seems to have adapted to almost every environment, from ridiculously hot springs at the bottom of the sea bed to barren ice fields to microscopic cracks in apparently solid rock far underground. Much of this life is, of course, far too small to see with the naked eye - bacteria or their cousins the archaea. Mammals are somewhat more limited; we don't find them inland in Antarctica, for instance. But what are the limits beyond which even the best-adapted mammals cannot live comfortably?

One of the easier limits to measure in this way is altitude. This is, after all, a fixed value, whereas factors such as temperature can vary throughout the year. Certainly, it would be useful to know whether a given species can survive as the world warms, but that can be a complex question to answer. When it comes to altitude, we simply have to go and look. For this reason, when describing the habitat of a creature in a conservation catalogue or the like, the altitudinal range of the animal is often described in numeric terms, while the preferred climate is described more vaguely.

Sunday, 18 September 2022

The Hybrid History of North American Deer

There are five species of deer native to the US and Canada. Two of these, the moose and the caribou, are distinctive animals with no especially close living relatives. The elk, while perhaps not as distinctive in appearance as these two, is even more distant from the others in evolutionary terms. The other two, however, are the white-tailed deer (Odocoileus virginianus) and the mule deer (Odocoileus hemionus) which not only look similar to one another but are, indeed, each other's closest relatives.

When I discussed these two species in detail last year, I mentioned the existence of the "black-tailed deer" a subgroup of mule deer with tails of a more solidly black colour than others of their kind. The black-tailed deer are native to the Pacific Northwest and are generally considered to consist of two subspecies of mule deer that share a common ancestor that split off from other mule deer early on. Since are subspecies, not full species, it should come as no surprise to discover that they hybridise with other mule deer where the two come into contact, although, if anything, this happens more often than we might expect.

Sunday, 11 September 2022

Leaf-Eating Monkeys: Borneo and Beyond

Hose's langur
Borneo is the third largest island in the world (after Greenland and Papua New Guinea), being about 10% larger than Texas, and around three times the size of the entire UK. The interior is rugged and mountainous, especially in the north, and, in its natural state, almost entirely covered in dense jungle. This is a perfect environment for spawning new species, which can easily become isolated from one another and still have plenty of lush vegetation to feed upon. It's also ideal for hiding these species from naturalists so that it's possible that even the species we currently recognise from the island are not a complete list.

As was common at the time, several species were named in the 19th century, often by naturalists unaware that what they'd just described had already been named in some obscure source by somebody else. Even after the general taxonomic tidying up of the 20th century, however, no fewer than four species of the genus Presbytis - loosely speaking, the Indomalayan group of langurs - were still recognised as living on Borneo.

Sunday, 4 September 2022

600th Synapsida

The time has come around once again for my approximately biennial piece of navel-gazing, as I celebrate this blog reaching its 600th post, almost 12 years after it first started. Since the 500th post, the world has (mostly) emerged from the perils of COVID and now tends to have other issues on its mind that biological science is less likely to be helpful with - not that I deal with epidemiology or virology here anyway. But let's take the traditional look back at what did appear on the blog during that timeframe and, allowing for the fact that I usually pick the topic on the day the post goes up, what might be coming over the next two years.

Animal behaviour and evolution remain the two most popular topics of my posts, and it's unlikely that that's going to change too much. However, there were also several posts on sociability specifically, as well as things such as diet and habitat and a more than usual number of posts on anatomy. In terms of the types of animals covered, where posts were on a particular species and not part of an ongoing series, rodents top the list, followed by bats. These are, of course, the top two mammalian groups in terms of number of species, but, while rodents are relatively easy to study, bats are rather less so... but perhaps that just means that studies on them tend to stand out more and pique my interest.

Sunday, 28 August 2022

Fossil Martens... or Not?

When talking about fossil animals on this blog I often mention the earliest known example of a particular group. But this often hides a degree of uncertainty, or even controversy, because such the exact identity of such fossils can be difficult to pinpoint. That's partly because, being, by definition, older than other fossil examples of the group, they are also the most likely to be incomplete or poorly preserved. Often, since we're talking about mammals here, the "oldest known fossil" may consist of little more than a distinctive tooth. 

The second, and perhaps even bigger, problem is that the further you go back to the origin of a group the more it blurs into whatever preceded it. Even if we had perfect remains, or if we could travel back in time and see the animals in life, or take blood samples from them for genetic analysis, there would always be a question of what exactly we were looking at. Where do you draw the line when, in reality, one group will have slowly and perhaps imperceptibly, evolved into a newer one?

Sunday, 21 August 2022

Food for Thought

The word "primate" means "of the first order" and the group of mammals is so-named because, even in the days before evolutionary theory, it was recognised that this is the group that includes our own species. I've previously discussed how primates are distinguished from other mammals, and one of our identifying features is that we tend to have larger brains in proportion to our bodies. (Not uniquely so, of course, given the existence of dolphins and their kin, but certainly well above the average).

But why? What is it about the primate lifestyle that, over the last 60 million years or more, has resulted in them growing larger brains than other, similarly sized, mammals? This is obviously a significant question, since it relates to what is undeniably the key defining feature of our own species and might explain why our planet is inhabited by sapient urbanised monkeys rather than, say, sapient city-building cats. 

Saturday, 13 August 2022

Leaf-Eating Monkeys: The Leaf Monkeys of Sumatra

Black-crested Sumatran langur
When the system of scientific naming that we now use was first devised, all monkeys were placed in a single genus, Simia. The initial listing of names, from 1758, does not include any species we would now recognise as leaf monkeys but, as these were "discovered" over the next few decades, most were placed in Simia, although a few were placed in newly-created genera that contained other, more typically fruit-eating, monkeys. The first naturalist to create a genus specifically for what we would now describe as "leaf monkeys" was Johann von Eschscholtz, a naturalist who had served on a Russian expedition that circumnavigated the globe. His write-ups of that expedition included the first scientific description of the plantlife of California, but they also included the description of a new kind of monkey, which he felt was distinct enough to give its own genus: Presbytis.

That was in 1821, and, while various other naming schemes were suggested through the 19th century, for much of the 20th, all langurs were placed in Eschscholtz's genus as a group distinct from the colobus and other leaf monkeys. During the 1980s, however, the grey and golden langurs, and their various close relatives, were split off into the genera they now occupy, leaving relatively few species still with their older designation.

Sunday, 31 July 2022

Miocene (Pt 34): The First Kangaroos in Australia

Ekaltadeta
During the Miocene, Australia was further south than it is today. However, it seems that the generally warmer climate of the early part of the epoch more than compensated for this, since we know that there were already coral reefs off the coasts of the main continent and also of New Zealand, which is far too cold for such things today. At the dawn of the epoch, the continent seems to have been largely covered by open woodland but as the world warmed in the Middle Miocene, and Australia edged northward, it became not only hotter, but wetter, until tropical and semi-tropical rainforests became the norm. It was only in the Late Miocene, around 10 million years or so ago, that the climate started drying again, especially in the interior, and the dense jungle began to die away, leading the way for the formation of today's Outback in the following, Pliocene epoch - although, even at the end of the Miocene, the coasts were more heavily forested than most of them are today.

Sunday, 24 July 2022

How Big is a Small Whale?

The ongoing expansion of humanity has placed several animal species under threat of population decline or extinction, whether due to direct effects such as loss of wild spaces or more indirect ones such as climate change. (And a great many of these species are non-mammalian, of course, despite the focus of this blog). On the other hand, there have also been many conservation efforts that aim to restore, or at least preserve, species at risk. As I've previously described, for example, both black-footed ferrets and European bison went completely extinct in the wild during the 20th century, but are now back living in their original native habitats, if only in small numbers.

Not all such restoration efforts have been successful, and there can be many different reasons for this, not all of which are necessarily biological. Better then, of course, to try and prevent species from becoming endangered in the first place. For this reason, many species are protected even if they are not currently at risk. The more we can understand about these species, the better we will be able to keep them that way. 

Sunday, 17 July 2022

Leaf-Eating Monkeys: Golden Langurs and Silvery Lutungs

Golden langur
During the Ice Ages, it is thought that the early grey langurs, ancestors of the modern sacred langur and its kin, sheltered in southern India where the climate allowed the warm forests on which they rely to continue to flourish. A second group of langurs, which had originally diverged from the grey langurs over five million years ago, sheltered instead further east, and their descendants include the spectacled and "limestone" langurs that still live in that area today. At some point, however, both moved northward again, and they met up somewhere near Assam in northeastern India.

In this region, they remained separated by mountains and rivers, but the barriers were not perfect, and there is some evidence that the two hybridised, leaving a genetic trace in the non-grey langurs of the region. Certainly, while these descendants are close enough to the spectacled and "limestone" langurs to be placed in the same genus, they form the oldest branch within it, somewhat distinct from the others.

Sunday, 10 July 2022

The Dolphins of Switzerland

Kentriodon
The Mediterranean is very nearly an inland sea. Its only natural connection to the world's wider oceans is through the Strait of Gibraltar between Spain and Morocco, a passage just 13 km (8 miles) wide at its narrowest point and in places just 300 metres (1,000 feet) deep; pretty shallow as such things go. It's probably because of this that some of the larger whales that inhabit the Atlantic (blue whales, humpback whales, etc.) are rarely if ever seen venturing into its waters.

Dolphins are a different matter, with the majority of North Atlantic dolphin species also being commonly seen in the Mediterranean, albeit in some cases only in its most westerly waters. This includes some of the really big dolphins that we'd normally call "whales", such as the killer whale, and there are three species of genuine whale that live there, too. The connection between the Mediterranean and the Atlantic has not always been there, however; for a long time during the Late Miocene, the two bodies of water were separated by a land bridge between Spain and Morocco, entirely cutting the Mediterranean off until it ended in the cataclysmic Zanclean Flood

Sunday, 3 July 2022

Bats in the Fynbos

Lesser horseshoe bat
From a human perspective, the ability of bats to navigate in pitch darkness through the use of biosonar is undoubtedly remarkable. Not only do they have to be able to avoid obstacles, but also, in the case of the insect-eating species, to locate and identify tiny prey items against the background. Their ability to do this is affected by a number of environmental factors, and the exact nature of the echolocation calls, and how the bat interprets them, may affect which of those factors have the most influence.

For example, the distance that a biosonar ping can travel is affected by both the temperature and humidity of the air through which it travels. Since there are bats in almost every habitat suitable for insects to live, we might expect the way that they use their sonar to vary depending on the local climate.

Sunday, 26 June 2022

I Would Swim Five Thousand Miles...

Breeding can be an energetically costly business, whether that's the effort put into finding and attracting a mate, or that required to raise young. The latter is a particularly important factor in mammals, which can't simply lay eggs somewhere where there's plenty of food and hope that the hatchlings do well for themselves as, say, an insect might be able to. Therefore, we might well expect that mammals will feed more during the breeding season, to compensate for all that extra energy they will be using. 

For males, there can be a downside, in that all the time you are spending finding and eating food is time not spend wooing and mating with females. Thus, in animals such as deer, we may find that males actually eat less during the mating season than they do at other times because their mind is far too much on other things. But females, given the needs of both pregnancy and lactation, ought to be different.

Sunday, 19 June 2022

Leaf-Eating Monkeys: Treetops and Limestone Cliffs

Dusky langur
Although the term "langur" is perhaps most associated with the monkeys of India, the term has been used more widely to refer to a range of similar monkeys found to the east. In this sense, the term is really one of convenience, reflecting both the resemblance and the relatively close evolutionary relationship between the various monkeys in the group. However, the word "langur" itself comes from Hindi and Urdu which are, of course, not native languages of the lands to the east, so there has been a move in recent times to use more local names for some of the species. I'm going to stick with the names that seem to be most common in English language sources, but there is considerable variation and not always much consistency.

One of the better studied of these species is the dusky langur (Trachypithecus obscurus). These live in the Malay Peninsula, from the southernmost parts of Myanmar in the north, through southern Thailand, and across essentially the whole of Peninsular Malaysia. Over the last few years, a small number have also been spotted in residential areas of Singapore, presumably having swum across the Johor Strait from the mainland, but they are not native there. Although definitive genetic evidence is lacking, seven different subspecies are currently recognised, three of which occupy different regions along the peninsula, with the other four found only on certain small islands off the coast. 

Sunday, 12 June 2022

Miocene (Pt 33): Killer Armadillos and Far-travelling Raccoons

Lycopsis
As the Miocene epoch drew towards its conclusion, the island continent of South America drew steadily closer to its northern counterpart. The gap would not be fully bridged by land until a few million years later at the end of the following, Pliocene, epoch but, when it did, many of the peculiar mammals of the southern continent would die out, albeit in many cases it was the subsequent Ice Ages and/or the arrival of humans that truly finished them off. One group that survived the experience, and that is still around today, is that of the armadillos.

Even so, armadillos were more diverse in the Late Miocene than they are today. Probably the most distinctive were the glyptodonts, which had solid, often domed, shells without the flexible bands seen in living armadillos. As the sweltering heat of the Middle Miocene faded towards temperatures closer to those we see today, grasslands began to extend across much of the southern part of the continent, and the glyptodonts adapted to it, switching towards an even more heavily grass-based diet than before. The resulting group of what we might loosely call "advanced glyptodonts" was the one that would later briefly cross over into the north and includes the most famous examples. In addition to certain features of their shell, they were distinguished by having teeth especially suited for chewing, with the high crowns suitable for grinding up grass and other tough vegetation.

Sunday, 5 June 2022

Ticked Off

Predators are not the only creatures to feed off other animals. Certainly, if you're an antelope, the obvious things to fear are lions, crocodiles, or whatever else might seek to ambush and eat you. But virtually all animals, and certainly all mammals, also suffer from parasites, a rather more insidious threat.

Very broadly speaking, parasites employ one of two tactics. Endoparasites live in inside an animal, often in the gut if they're any larger than single-celled organisms, although they can infect other organs. These are typically parasitic "worms" of one kind or another, and fighting them off is more a matter of an animal's immune system than of any behavioural traits (at least, once it's already infected). Ectoparasites, on the other hand, live on the outside of an animal, clinging to the skin and perhaps hiding among the fur. Fleas are an obvious example of this sort of parasite and grooming can be at least a partial defence against them.

Saturday, 28 May 2022

When White-footed Mice Invaded Michigan

When I'm describing a particular species of mammal on this blog, one of the first things I usually mention is where in the world it lives wild. Clearly, there are differences in the fauna of different continents or specific islands. Cougars, black bears, pronghorn antelope, and coyotes are all common enough in the US, but don't live in Europe. We have Eurasian and Iberian lynx, but not bobcats and Canada lynx. There are bison in Europe, but they're a different species than the American sort, and we only have wild raccoons because some were deliberately released in Germany in 1934. 

Clearly, the existence of the Atlantic Ocean is not to be sniffed at. However, this applies on a smaller scale, too, where some physical barrier that's some way short of an ocean, but is still significant, prevents an animal from advancing further across its home continent than it might like. 

And then there's the fact that animals have particular requirements as to the climate and vegetation of their native areas - even if the vegetation is only affecting the prey animals that they themselves need to feed on. The difference between this and the physical geography of rivers, mountains, and so on, is that it's changing over a much faster timescale, especially in recent decades. Animals may be forced to move to new areas, which can be a problem if the physical geography prevents them from doing so and can be a problem for other reasons even if it doesn't.

Sunday, 22 May 2022

Leaf-Eating Monkeys: Sacred Langurs of India

Sacred langur

In Hinduism, the monkey god Hanuman is a companion of Rama, one of the more popular incarnations of Vishnu, and represents, among other things, loyalty and virtue. The specific type of monkey most associated with him is known by various names, including "Hanuman langur" and the rather uninspired "northern plains grey langur", but I'll stick with sacred langur (Semnopithecus entellus).

As currently defined, the sacred langur is found across almost the whole of northern India where suitable habitat exists. The biggest limitation to that habitat is elevation; sacred langurs are very much a lowland species, not found above about 400 metres (1,300 feet) - which cuts out rather a lot of the more northerly parts of the country as it reaches towards the Himalayas. Other than that, they require forest, but they seem adaptable to different types. 

In practice, they mostly live in dry tropical deciduous woodland because that's largely what there is in that part of the world, but they extend into thorny scrubland in the northwest near the deserts of Rajasthan and into damper forests in the east. They are also common, probably due in part to their reputation as a sacred animal, on the outskirts of densely settled urban areas. A population is also found in southwestern Bangladesh, but they aren't thought to be native there and were likely brought across by Hindu pilgrims in the late 19th century.

Sunday, 15 May 2022

The Last Pangolin in Europe

Ground pangolin
Pangolins are undoubtedly odd creatures. Most obviously, there's the fact that they are covered with an armoured sheet of keratinous scales, making them look somewhat like an animated pine cone. No other mammal has this feature or anything much like it. But, even ignoring this, they are still unusual, with their narrow diets, conical snouts, digging claws, and long, broad tails. 

The animals that they most resemble are probably anteaters, especially the smaller species. At one time, they were even classified together with the anteaters, but there are some significant skeletal differences, especially in the structure of the backbone that indicate they are clearly distinct. Furthermore, anteaters originated in South America, while pangolins are known only from Africa and Asia, so it's long been recognised that the resemblances are actually due to parallel evolution, with the animals having a similar diet.

Sunday, 8 May 2022

Spotting Ocelots

There are a number of different species of cat living in South America, including some that are not widely known by the general public. Across much of the continent, however, the most abundant are often the ocelots (Leopardus pardalis), outnumbering both the larger cats that require substantial food resources and the smaller, more localised ones. Aside from the desert regions west of the Andes, ocelots live across almost the whole of the continent from northern Argentina to the Caribbean coast and their population is large enough that they are not generally considered a threatened species.

But that broader picture, which is generally positive for the species, hides some local variation. They are not, for example, especially common in the Caatinga, the area of dry scrubland that covers the easternmost regions of Brazil. More significantly, perhaps, they also become less progressively common once you leave South America and head north. Ocelots are found throughout Central America, and along both coastal regions of Mexico, and they are even found in small numbers in southern Texas and Arizona. In both of these latter countries, however, their populations are low enough that they are listed as endangered species by the local authorities responsible for such matters - the US Fish and Wildlife Service and the Secretariat of Environment and Natural Resources.

Sunday, 1 May 2022

Bats in the Megafire

A little over ten years ago, I wrote on this blog about the effect of forest fires on bats in Florida. It turned out that the bats in question, which were big brown bats (Eptesicus fuscus), one of the most common bat species in the US, were actually quite happy when forest fires tore through the sandhills where they lived. This is because it improved their environment, in particular making it easier to fly about through what might otherwise be a mass of tangled vegetation and thick undergrowth. 

That was a decade ago, and further studies since that date have broadly confirmed the findings of the one I was referring to in that post. A 2019 study, for example, showed that the same was true for a number of species in Australia. Overall, it seems that, at worst, forest fires have no overall effect on bat populations and, in general, they're actually a benefit.

Sunday, 24 April 2022

Leaf-Eating Monkeys: Red and Olive Colobuses

Zanzibar red colobus
The strict food requirements of red colobus monkeys make them one of the most endangered groups of African primates but they are still found across a surprisingly wide swathe of the continent. While we used to recognise only three or four species (albeit with many subspecies), it has become clear over the last thirty years or so that there are many more, around half of which are now restricted to very small areas. In most cases, this is because of the obvious reason that their old habitat has been destroyed and that they used to range further afield. Some, however, have never strayed far from home.

The easternmost species of red colobus falls into this latter category. Named the Zanzibar red colobus (Piliocolobus kirkii) this has historically restricted to the eponymous island. Since 1964, this has been the "zan" part of Tanzania, and lies just over 20 miles off the east coast of the mainland with an area of a little under 1,500 km² (565 square miles). With a human population of around 1,500,000 it is, as one might expect, substantially given over to agriculture and other development. As a result, while they once ranged across the island, they are now primarily found in the less settled eastern half of the island, where there are some inland national parks. In the 1970s, a small population was re-introduced to a patch of land on the west coast north of the main urban areas and others were translocated to Pemba Island to the north, where the species has never existed naturally. While one of the latter groups did survive and breed, their descendants are likely quite inbred and it has been argued that we'd be better off supporting the main population in their original home.

Sunday, 17 April 2022

Miocene (Pt 32): Time of the Sea-Sloths

Pronothrotherium
In the absence of the sorts of herbivore more familiar to us today - and already current in the Northern Hemisphere of the day - the large herbivores of Late Miocene South America were nonetheless varied. Many took up habits similar to those of their northern counterparts, so that, at a brief glance, they would not necessarily have appeared so odd to a passing time traveller. 

The mesotheres are a possible case in point. They were a group of notoungulates, one of the two orders of native hoofed mammal that had survived into the Late Miocene along with the litopterns. Earlier in the Miocene, they had perhaps looked even less remarkable, digging herbivores of a similar size and shape to wombats. But as the epoch wore on, they gradually increased in size, while still retaining the adaptations to digging, which they would likely have used to get at tasty roots, and possibly for constructing burrows in which to live.

Sunday, 10 April 2022

Monitoring Mandrill Movement

Understanding how animals move about during their daily lives can be important for a number of reasons. It's a crucial part of their behaviour and ecology and, perhaps more significantly, it can provide information that we need if we are to help conserve those that are endangered. How much space do they need? What sort of places do they go to that we might need to ensure they have access to? And so on.

There are many ways of determining where animals travel on a regular basis and different methods will work better for some animals than they do for others. For example, we hear a lot in modern times about the use of remote telemetry, attaching GPS tags to animals and watching to see where they go. This is a useful technique, especially for tracking long-distance migrations. But it still requires that you capture your animal to fit it with the tag and then hope that having the thing attached won't affect its behaviour... which may, in turn, depend on how large it has to be. Not to mention the risk that it might fall off.

Sunday, 3 April 2022

Wolves at the Campfire

There's an internet meme, which exists in several different variants, that makes a half-serious joke about dog domestication. A typical version shows a picture of a wolf ostensibly heading to a camp of stone age hunters, hoping to get some food, and thinking "what's the worst that could happen?"... followed by a second picture captioned "thousands of years later" and showing an inbred domestic dog dressed in ridiculous knitwear. The second part is an accurate enough description of what thousands of years of domestication and directed breeding have done to at least some dog breeds. 

But what about the first part? That's showing what's probably a common understanding of how wolves originally became domesticated and turned into dogs. Essentially, dogs domesticated themselves, with those wolves that were least wary of humans, due to whatever quirk in their individual personalities, being the ones most likely to get close to them. Over time, there was further selection in this direction, with the friendliest wolves also becoming the most popular/useful to the humans until, eventually, domesticated breeding was able to take over. 

Saturday, 26 March 2022

Monster Birds of South America

Teratornis
Yes, it's that time of year again. This post will be current as of 1st April, and that means it's time to hand over to... birds!

The largest birds, both living and extinct, are flightless. This is hardly surprising, since being small and light is a considerable boon to anything that wants to get off the ground. Nonetheless, there are some really big birds that can, in fact, fly. Going by wingspan, rather than body weight, the largest flying bird alive today is the wandering albatross (Diomedea exulans). In second place, and also the third-heaviest of any flying bird behind a couple of species of bustard, is the Andean condor (Vultur gryphus). This has a whopping wingspan of up to 310 cm (10' 2") and North Americans probably won't be surprised to discover that the California condor (Gymnogyps californianus) isn't far behind.

The Andean and California condors are, indeed, each other's closest relatives. They are both members of the New World vulture family, which also includes such things as the widespread turkey vultures. They are distinct from the Old World vultures, which are members of the hawk family, although they're very much in the same corner of the bird family tree.

Sunday, 20 March 2022

Leaf-Eating Monkeys: Red Colobuses of Central Africa

Ashy red colobus
The problem with being a primate subsisting primarily on leaves is that, on their own, they aren't very nutritious. Humans on a vegan diet can hardly be expected to live on lettuce alone; they need grains, pulses, nuts and so on, and we have the advantage of cooking making much of our food easier to eat and digest. Colobus monkeys have complex digestive systems that allow them to extract more nutrition from leaves than a primate would otherwise be able to, so they have the edge over us in that respect, but they still require plenty of fresh leaves and this leads to the more exclusively folivorous ones having specific habitat requirements that leave them vulnerable to any degradation or loss of their environment.

The end result of this is that many colobine monkeys are endangered. In Africa, the most endangered group, and probably the most threatened group of primates of any kind on the continent are the red colobuses.

Sunday, 13 March 2022

Vishnu's Otter in Bavaria

Otters are members of the weasel family, something that has been recognised since the dawn of taxonomy in 1758, when Linnaeus placed them in what was then the weasel genus (taxonomic families not yet being a concept). Their adaptations to the water, including their powerful muscular tails, were long thought significant enough that they were separated out into a distinct subfamily, a position they still retain, although it turns out that they are more closely related to the weasels proper than to some other members of the family such as, say, pine martens or wolverines.

Perhaps because rivers are a good environment for forming fossil-bearing sites, we know of a significant number of fossil otters and, most of them would doubtless have been instantly recognisable as otters were we able to see them in the flesh, there is perhaps more variety amongst them than we might at first expect. For example, a number of them are quite large - in some cases, larger even than the "giant otter" (Pteronura brasiliensis) of today's Amazon, the largest living member of the weasel family. (So, yes, it's bigger than a wolverine).

Sunday, 6 March 2022

Moving Away From Home

One common feature among many mammal species is that, once they become old enough to do so, they leave home to find a place to settle for themselves. Often, it's the young males that travel the furthest, and in animals that live in herds, colonies, or other groups, the females may not disperse at all, creating a matrilineal society - interestingly, the opposite is generally true in birds. This discrepancy between the sexes ensures that when the males do find somewhere to settle down, the females that will become their new neighbours or pack-mates will not also be their own sisters and other close relatives.

But there are other reasons why animals might choose to disperse, sometimes moving from one location to another once they are already adult. This may be due to some sudden disruption in their original habitat, or to longer-term effects, such as climate change. Either way, while it's not an easy subject to study in the wild, understanding the causes and practices of animal dispersal can be important for issues such as conservation and understanding wider population dynamics. 

Sunday, 27 February 2022

Leaf-eating Monkeys: Black-and-White Colobuses

King colobus
The Old World leaf-monkeys are formally known as "colobine" monkeys, with the name of their subfamily coming from what British zoologist Thomas Jerdon considered to be the most typical member of their subfamily when he first named it in 1867. These, of course, are the colobus monkeys, of which there are a great number of species. Jerdon, however, was thinking in particular of what we would now call the black-and-white colobus monkeys, so it's these against which, taxonomically speaking, all other leaf monkeys are compared.

The first colobus monkey of any kind to be scientifically described was the animal now known as the king colobus (Colobus polykomos). This was in 1780, with Eberhard von Zimmerman basing his description on a specimen collected from an island off Sierra Leone. His original name meant something like "many-singing monkey", and it was only in 1811 that the word "colobus" was coined. This comes from the Greek word for "maimed" and refers to the fact that colobus monkeys have no visible thumbs, just a small lump on the side of the palm, making it look as if they have been cut off.

Sunday, 20 February 2022

Miocene (Pt 31): Terror Mice and the First Howler Monkeys

Phoberomys
As the heat of the Middle Miocene gave way to the more moderate temperatures of the Late Miocene, grasslands grew across much of the Northern Hemisphere. In South America, however, the changes were, perhaps, less significant due, in part to its more equatorial position. Nonetheless, even aside from the general worldwide cooling trend, the South American climate was changing as the Andes continued to rise, affecting weather patterns across the continent. It was also continuing to edge closer to North America, so that, towards the end of the epoch, it became possible for a few animals to make the crossing using the islands of what is now Central America as stepping stones.