From the Iowa Department of Natural Resources
-- A cooperative joint venture between Iowa DNR and Iowa State University hopes to capture and install radio transmitters on white-tailed jackrabbits living at ISU’s Agricultural Research Farm.
Scientists hope future radio monitoring will enable researchers to collect long term data regarding the survival, habitat use, spacing, reproduction and nocturnal movements of the state’s only species of wild hare.
Amazingly abundant during the 1950s and 1960s, jackrabbit numbers have shown a steady and alarming decline during the past four decades. Today, they have nearly vanished from the state.
“Capturing live jackrabbits for the study has presented an extraordinary challenge,” says DNR Wildlife Technician, Mark McInroy. “Lately, we have gotten a few good breaks though. Recent cold weather has actually boosted our success as jackrabbits become more willing to visit the piles of corn we’re using as bait. Once they come in and begin feeding, we attempt to capture the animals with remote controlled drop nets. We’ve tested a lot of different capture methods, and the drop nets are the most effective technique we’ve tried so far.”
Rarely active during the day, jackrabbits are highly nocturnal creatures. Successful capture requires late hours in the field. With nighttime temperatures routinely dropping to minus double digits, thick mittens and multiple layers of thermal clothing are a must for humans seeking to capture the wild hares.
“Although we collect weights, measurements, and DNA samples from every jackrabbit we can put our hands on, our main emphasis is on the capture of females,” McInroy said. “Females have the potential to yield the greatest amounts of data and, as they begin to produce young this spring, they are also the ones who can lead us to more samples. Once the radio transmitters allow us to accurately pinpoint nest sites we’ll quickly move in on the babies which, for the first day or two, are much more vulnerable to capture. If we’re successful, the young will also be marked with tiny lightweight ear tag transmitters. By marking day-old youngsters at the nest, we hope to significantly expand our data collection.”
“Right now there is a lot that we don’t know about Iowa jackrabbits; a lot we don’t know about the basic life history characteristics of these animals,” said Maggie Brandenburg, a student researcher with the ISU Department of Natural Resource Ecology. Brandenburg is simultaneously conducting an independent companion study of the Ames jackrabbits.
“Next spring, we’ll be following the radio collared females to see where they travel, what habitats they use, how those habitats are connected, how big their home range is and what kind of habitats a female selects when rearing her young,” Brandenburg says. “We’ll also be looking at how many litters a female produces during a season and how many young are produced in each litter.”
“I think the DNA sampling is another very important component to understanding what’s really going on with this species,” McInroy explained. “We know that we still have several pockets, or island populations, of white-tailed jackrabbits scattered across the state. At this point, we assume that these populations are totally isolated from others and that inbreeding is occurring. If so, it’s not a good situation. But if we discover that populations are mixing, then that would be a very pleasant surprise. By looking at DNA we can go from guessing to knowing.”
“We’re looking at a lot of different things,” says Brandenburg. “Our hope is to find something that will keep jackrabbits from disappearing in Iowa.” Iowa’s first of its kind, jackrabbit research study will be showcased in the May-June issue of Iowa Outdoors Magazine, the DNR’s flagship publication of conservation and recreation. Visit the magazine on line at www.iowadnr.gov.
-- By Lowell Washburn