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

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

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

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.

Sunday, 13 February 2022

Are Animals Darker in the Tropics?

In 1833 Prussian ornithologist C. L. Gloger published the book Das Abändern der Vögel durch Einfluss des Klimas (roughly "the modification of birds by climatic influences"). In this, he put forward a proposal that the plumage of birds living in hot, humid, environments tends, on average, to be darker in colour than that of those which do not. In 1929, biologist Bernhard Rensch formalised this as "Gloger's Rule", one of a number of zoological "rules" that seemed to be true more often than not but for which there was not necessarily a clear explanation.

Crucially for this blog, it seemed to be true of the skin and hair of mammals as well. This observation raises a number of questions, of which the first is clearly "is it true?" 

Sunday, 6 February 2022

How Dolphins Got Their Large Brains

As a rule, larger animals tend to have larger brains, just as they have larger hearts, livers, and other internal organs. But the relationship is not a linear one, partly because, unlike the liver, there's a minimum size below which the brain doesn't have room for the basic housekeeping functions that keep the body ticking over, so that small animals have proportionately larger brains than large ones. If we want to know whether a particular creature has a larger, or smaller, brain than we'd expect then, as I've described before, we use a mathematical formula called the encephalisation quotient to determine what the size of the brain "should be". 

By definition, an average mammal should have an EQ of 1. The formula breaks if we try to apply it to non-mammalian animals, such as birds, probably because their brain architecture is different from ours at quite a fundamental level. Even for mammals, there is some debate as to exactly what formula we should be using; most older studies have determined that brain size typically rises as the 2/3 power of body size (that is, as the cube root of the square) but a 2019 study argued that it's perhaps more accurate to base it on the 3/4 power and this seems to be a growing consensus.

Saturday, 29 January 2022

Monkeys with Many Stomachs

Rhesus monkeys have entirely
normal stomachs
The word "monkey" entered the English language relatively late, in the 16th century. It's not at all clear where it came from, and it doesn't have a direct counterpart in most other European languages. Instead, they, like medieval English, used the same word for both monkeys and apes (and that word was, in our case, "ape"). From a modern, scientific, point of view, these other languages are correct, because there is no scientifically definable group of animals that fits with what most people mean by "monkey".

This is due to the rule, often mentioned on this blog, that the members of any scientifically defined group of animals have to be more closely related to all the other members of that group than they are to anything else. The diagram further down this post showing how all the major groups of simian are related illustrates why this is. At the top, we have the macaques and the leaf monkeys, both of which are indisputably monkeys. But their closest relatives are the apes (which, of course, includes gibbons as well as "great apes"). Only then do we get to the other monkeys, which means that, for example, a macaque is more closely related to a gorilla than it is to a marmoset.

Sunday, 23 January 2022

Out of the Amazon: A History of the Opossums

Tate's woolly mouse-opossum,
a marmosin species
When most people think of marsupials, it's likely that Australia is the first place to spring to mind; the land of kangaroos, koalas, and wombats among many others. In fact, even the "Australian" marsupials aren't restricted to that country, since they are also found further north, notably in New Guinea - which, for example, has its own species of wallabies. But, more significantly, marsupials are also found outside of Australasia, in the Americas.

The best known of these American marsupials is surely the Virginia opossum (Didelphis virginiana). This lives across most of the US outside of the western mountains and interior deserts, and is also found just across the border in parts of southern Canada, through the whole of Mexico, and well into Central America. It's the only species of opossum found north of Mexico, but it's very far from being the only species of opossum anywhere.

Sunday, 16 January 2022

Why Animals Have Whiskers

One of the key defining features of mammals is that they have hair, or are at least descended from other animals that once had hair. The primary purpose of hair is to keep the animal warm, something useful for any warm-blooded animal, especially if it's small (elephants and rhinos, for example, while they do have hair, aren't really what you'd call "furry"). But, over millions of years of evolution, hairs have also evolved to carry out other functions, such as the protective spines of hedgehogs and porcupines.

Another example of specialised hair is that of whiskers. Technically known as vibrissae, whiskers are remarkably common in mammals. When we think of whiskers, it's likely that most people's thoughts jump immediately to the long, mobile, whiskers of cats and mice. But whiskers can also be shorter and less mobile than this, as we see in such animals as horses. Indeed, even if we look at a cat, whiskers are not restricted to the long ones on the snout; they also have whiskers on the eyebrows, on the cheeks and chin, and on their forelegs just above the paws. 

Sunday, 9 January 2022

The Social Lives of Giraffes

Many of the cloven-hoofed mammals are herd animals, living in large groups that typically have dominance hierarchies and other relatively complex internal structure. We see this in both of the main families of such animals: the deer and the "cattle family" (which includes goats, sheep, and antelopes besides the obvious). On the other hand, there are certainly plenty of exceptions. Smaller deer, such as muntjacs, for instance, tend to be relatively asocial, apparently gaining more benefit by hiding from predators than they would from living in large and watchful, but visibly obvious, herds.

But it isn't just the smaller cloven-hoofed mammals that can lack sophisticated social lives, because the same also seems to be true of the largest of all such animals: the giraffe (Giraffa camelopardalis). At which point, I should probably take a brief diversion to explain what a giraffe is, and where it fits in the larger mammalian family tree.