LONGVIEW, Wash. (AP) — An effort to re-establish a population of endangered Columbian White-tailed deer at the Ridgefield National Wildlife Refuge is off to a shaky start, but biologists remain hopeful that fawns born this spring will live through the summer, and become established at the refuge.
To help them survive, U.S. Department of Agriculture contractors have begun killing coyotes.
In April, biologists working for the U.S. Fish and Wildlife Service used drop-nets and dart-nets to capture and relocate 12 deer from the Julia Butler Hansen Refuge near Cathlamet to Cottonwood Island in the Columbia River, with 35 others moved to Ridgefield.
Scientists were worried that the JBH refuge could flood, and hoped the move would help grow herds in the new locations.
Eventually, biologists hope Ridgefield will support a population of at least 80 White-tailed deer.
But the deer at Ridgefield have struggled to adapt. As of late July (the most recent information available) a total of 13 relocated deer had perished, and seven of the 22 surviving deer have moved off the refuge, refuge manager Chris Lapp said recently in a phone interview.
Most of those deer perished within a couple of months of the move.
"I'd say about 90 percent of them were kind of up front — immediately after. ... The rate seemed to spike within that time period, then dropped off," Lapp said.
Biologists fully expected some deer to fall prey to the heightened stress and disorientation associated with relocation — and several did. But "a very healthy and robust" coyote population on the Ridgefield refuge is responsible for about a third of the deaths, Lapp said.
Because the herd was smaller than expected to begin with (scientists had initially hoped to move 50 deer to Ridgefield, but capturing that many deer proved to be more difficult than expected), the herd is now more vulnerable than scientists would prefer, Lapp said.
"We are at the point now where we really can't lose any more. We are trying to get a population established. Numbers are everything," Lapp said.
This summer, contractors from the USDA Wildlife Services program began trapping and shooting coyotes on the Ridgefield property to improve the deer's chances of survival.
Pregnant does and young fawns are especially vulnerable during spring and summer. If young deer can make it to the fall, they become fast and savvy enough to avoid coyotes, thus increasing the herd's chances of survival, Lapp said.
"We saturate our predator removal efforts just before fawning occurs (and) through the fawning period. We'll pull back when fawns become self-sufficient as fall approaches," Lapp said.
So far, 13 coyotes have been killed.
According to the USFWS Environmental Assessment, a document that outlines the plan for moving and protecting the deer, coyotes are a "major" obstacle to establishing a sustainable population.
For example, one 2010 study conducted at the JBH refuge indicated that coyotes were responsible for 69 percent of deer mortalities. Coyote populations are believed to be even bigger at Ridgefield.
The plan calls for predator removal to be implemented whenever the ratio of fawns to does drops below a safe level, or when the overall deer population is below about 60. Coyotes will be killed until the goal population of 80-100 deer is sustainable.
Researchers won't know until this fall how many fawns survived the summer. Newborn fawns aren't tagged or collared, and they're difficult to spot when brush is dense during the warmer months. But researchers will begin monitoring them more intensely later this year, and that data will help scientists have a better idea of the herd's future.
Despite the initial setbacks, Lapp said the effort has helped wildlife managers learn about relocating an animal population and about White-tailed deer behavior.
Each of the relocated deer has displayed a unique response to the move, Lapp said.
"There is no consistency. Each deer has their own personality. There are deer that have hardly moved. They've settled in and taken the refuge as their home and seem to be very stable. There are other deer that swam across the Columbia and took refuge on Sauvie's Island. Then there are a handful of deer that move all over the place — as far as Woodland. ... It's a very interesting insight into deer behavior — I would not say they all act the same," Lapp said.
Information from: The Daily News
Copyright 2013 The Associated Press.