Search This Blog

Monday, April 11, 2016

Studying the Unseen
This Sumatran tiger was snapped by a camera trap in Indonesia by Steve Winter, a National Geographic wildlife photographer.

Recently, the world of big cat conservation got some rare good news.  For the first time since scientists actually started counting a century ago, the number of wild tigers in Asia has actually increased.  A good-sized majority of wild tigers are in India, with most of the others in the immediately adjacent countries.  These represent the Bengal tiger subspecies, which has always been the most common... not the being the "most common" tiger is anything to brag about.  It's sort of like being the wettest desert.  Amid all the good news, there was a bit of a damper.

Cambodia, it seems, is now tigerless.

Now seriously, you may wonder, how can you tell?  I could have spent a decade living in Cambodia and never seen a single one.  The tigers of Southeast Asia are cats of the rainforest, and even though rainforests are full of animal life, you almost never see it.  I've spent a week hiking through an African rainforest, and I saw wild mammals once - a troop of black-and-white colobus - for all of sixty seconds.  I recently visited a Central American rainforest and had slightly - slightly - better luck, but only because I spent most of my time along a river, and animals have to drink.  The truth is that, except for large grassland mammals, wild mammals are extremely hard to find.  Especially when they go out of their way not to be seen, as tigers are wont to do.

Not only are they hard to see, but even if you do see them, they can be difficult to tell apart.  You drive to work one morning and see a herd of deer in a field alongside the road.  On the ride back home that evening, you see a herd of deer in that same field.  Are they the same deer, or different ones?  Without knowing, it can make it very hard to determine how many members of a population there are.  And without even knowing how many animals there are, how can you know which species are even endangered?

For some species, especially those living in open areas and congregating in large groups, scientists have the luxury of going out and actually counting.  The hope of many scientists is to capture a few members of their target species and radio collar them, which will allow the scientists to track the movements of the animal and understand how it uses its environment.  Especially important to learn from this - how much space does the animal require, and therefore how many members of that species can a protected area sustain.  Actually getting your hands on an animal also provides opportunities to collect physical data, such as weights and measurements, as well as DNA samples.

In other cases, alternative methods of study have to be employed.

A popular tool is the camera trap, a motion-sensitive camera that can be left out in the wilds.  When you go back to check on it, you can see what creatures came and went while you were gone, including animals far too wary to come anywhere near a blind.  It had the advantage of recording everything that comes by, so you may get images of animals that you totally weren't expecting to see.  You'll also get people - poachers and illegal loggers have been caught in the act on these camera traps (which is why they tend to destroy them if they find them).

With pictures, it becomes possible to start to identify individual animals based on their size, sex, markings, patterns, and scars.  Field biologists collect their photos in books that resemble those which police officers used to house mug shots in.  When they sight an animal, or get an incomplete image from a camera trap, they can compare them against these photo books to try and identify it.  Knowing how many members of a species are frequenting an area tells us a lot about population density and social organization.  Having images of mothers with offspring, or of courtship and copulation, can help us understand the relatedness of individuals in the population.  Keeping track of individuals over periods of time can tell us about survivorship.

Some animals are too wary, too elusive to even be caught by the camera traps.  For those, scientists can use indirect methods of monitoring the species.  Footprints, fecal samples, and other markings - such as the claw marks that forest cats often leave on tree trunks - can provide some information.  For some species, especially birds, recordings of vocalizations can be played in hopes of getting hidden animals to call back and reveal themselves.  Footprints tell us how big the animal was, and sometimes can be used to identify individuals.  Dung tells us what the animal has been eating, as well as serving as a source of hormones and DNA samples.

A fancy new tool that some scientists are employing - including in Southeast Asia, where tigers still roam - is the humble leech.  Many animals are good at avoiding scientists but no one is good at avoiding leeches.  Leeches, of course, suck blood, and blood has DNA.  Biologists have learned that by collecting leeches and extracting blood from their guts, they can determine what animals the leeches have been feeding on; collect enough leeches and you get a decent DNA sample of the species that frequent that area.  It sort of reminds you of the whole mosquito-in-amber bit from Jurassic Park.

The only leech exhibit I've ever seen, at Oglebay's Good Zoo

Zoos and aquariums have assisted field biologists by offering up their animals as test subjects.  Have a radio collar that you plan on using on bush dogs, virtually neck-less wild canines from the jungles of South America?  Before you put one on a wild bush dog and turn it loose, uncertain as to whether it will stay on, or get chewed off by the rest of the pack, or fizzle out as soon as the dog enters water (as they love to do), test it on zoo specimens.  Need DNA samples of various species to have a baseline to compare the findings from your leech study with?  Zoo and museum specimens can help!  Best method for sedating a rhino?  Ask a zoo vet!  Need an audio library of tiger vocalizations to help with your study in the wild?  Go to the zoo!

By collaborating, zoos, aquariums, museums, and conservations involved in field research can use their combined expertise to learn more about animals in the wild and how to protect them.  In turn, knowledge gained by studying animals in the wild can be used to help zoos and aquariums improve care for their animals.

No comments:

Post a Comment