Carnivore research helps scientists protect carnivores and their habitat. Some research questions cannot be answered adequately through the use of non-invasive research methods. For more specific data collection, scientists must sometimes use invasive research methods, meaning that individual animals must be handled by humans. Scientists do not take the decision lightly because they know the risk to the animals; keep in mind that most people go into wildlife biology because they care deeply about wild animals.
At Santa Monica Mountains NRA, wildlife biologists were tracking bobcats and cougars within the park and in the suburban areas surrounding the park. They needed to know whether bobcats were using the patches of undeveloped land between housing developments. They wanted to know how mountain lions were coexisting in the park, which is too small for a large population of such large carnivores, but is cut off from larger areas of habitat by large freeways. They particularly wanted to understand why bobcats in the park and urban surroundings were dying off due to a mange epidemic; what in their environment might be making them susceptible to such bad mange afflictions? I spent three months as a volunteer wildlife biologist at the park helping study the park’s carnivores (and lizards, but that’s another post).
Radio telemetry allows biologists to track individual animal movements
Biologists can follow the movements of a specific animal using radio telemetry. Biologists track the signal transmitted by a radio collar on the animal using a hand-held antenna. Through headphones, the biologist listens for the clearest signal and takes a compass bearing. Then they move a good distance away and get a second bearing, then a third, to triangulate the animal’s position. The more points, the more accurate the location. Sometimes, terrain prevents the biologist from getting all the way around the animal or affects the signal.
Biologists get to know the individual animals; they need a starting point each day to look for the animal, so they have to know their range and habits to predict where they’re going to be.
Sometimes you know you’re spitting distance from the animal, but you still can’t see it. Sometimes you just can’t find them, despite driving circles around town listening for a faint signal through the static.
Fancier models of collars cut out the biologist man-hours and offer more accurate and frequent data by allowing satellite or GPS tracking. Where budget is low but volunteer/grad student biologists are available, researchers may choose to use the more affordable collars so they can track more animals. Satellite and GPS collars may also have shorter battery life and be heavier than traditional collars.
Of course, for biologists to follow the signal from an animal, they have to catch the animal first and given a radio collar.
To be tracked with radio telemetry, animals must be captured and collared
Carnivores are elusive and challenging to trap. Biologists captured two mountain lions while I was at Santa Monica Mountains NRA, but hadn’t captured one over the previous year of trapping efforts. Live trapping is an enormous effort, requiring massive man hours (and lots of ‘trap nights’ – the number of nights the trap is open for animals).
Much effort is put into attracting animals. Trap locations are carefully selected, preferably placed along game trails that the carnivores might use, or even better, where signs of the species have been detected before (scat, sightings, tracks). Traps are disguised as best as possible with dirt, leaves, and branches from the site. To draw carnivores despite the smell of humans, specially-crafted scent concoctions called “lure” are smeared in the vicinity.
For bobcat trapping at Santa Monica Mountains, we also used “live bait” in the form of doves, which were placed in a separate portion of the cage where bobcats could see but not reach the birds. The birds were a lot of extra work. Every day biologists (often volunteer interns like myself) checked the traps and fed and watered the birds. The birds only stayed out for a couple days at a time before being brought in, but of course required daily feeding regardless.
Minimizing harm to captured animals
To minimize danger to the carnivores from being without water or food for too long, the traps are checked first thing in the morning. So every night the traps are open requires several hours from multiple staff people.
The sedation period is the danger period for the animals. Biologists are very careful to administer the appropriate amount of sedative. While under sedation, wild cats are at risk of overheating, and their temperature is carefully monitored the entire time they’re unconscious. One mountain lion was trapped on a hot morning, so we had to keep pouring cold water over its stomach to keep its temperature down. When a wild cat is coming out of sedation, biologists have to make sure it isn’t cutting off its air by leaning its throat on the collar.
Collaring the captured animal
Radio collars are expensive and only last a limited amount of time (up to a few years). Due to their price, cash-strapped researchers are limited in the number of animals that they can collar and track. Gathering enough statistically significant data can be a challenge with such a small sample size.
Trapping animals also allows collection of physical data
Because animals are captured so infrequently, biologists collect as much data as they can. When an animal is captured, biologists have a very short timeframe to collect data because they cannot risk leaving the animal sedated too long – under an hour. An all-hands call summons a huge crew of biologists to collect as much information as possible.
Data are collected on the animal’s weight, size, teeth, and pads. Blood is often drawn to gather genetic information and test for diseases.
Part 3: Invasive Survey Methods (this post)
Part 4: Carnivore Conservation in Cascadia