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.