Showing posts with label Coluber constrictor flaviventris. Show all posts
Showing posts with label Coluber constrictor flaviventris. Show all posts

Saturday, August 20, 2011

The Eastern Yellow-bellied Racer in Saskatchewan

Photo Credit: Laura Gardiner
The following story is being carried by the CBC, Canada.

Wet weather in Saskatchewan is creating trouble for a dwindling population of racer snakes.

Their winter home, a den in the Grasslands National Park in the province's southwest, was hit with heavy rain last year and this spring, turning the site into a soggy and largely inhospitable mess.

The eastern yellow-bellied racer is the focus of study for University of Regina student Laura Gardiner.

"It looks like a big crater," Gardiner said, in describing the damage done to the snake pit. "The soil has just collapsed or slumped."

Gardiner said the damage is so severe some snakes were trapped in the pit and could not emerge from their winter hibernation.

To make matters worse, spring rains led to a second slump at the pit and those snakes that did manage to make it out will have difficulty finding an open route to take them below the frost line for this winter's hibernation.

Gardiner notes the den is home to a number of species of snakes, including racers and rattlesnakes.

"Eastern yellow-bellied racers are a threatened species already in Canada," she said. The Grasslands park had the largest known snake pit.

"What the slump has done is prevented the snakes from the coming out and likely caused death for some of those snakes," she said.

As part of her research, Gardiner has been tracking the snakes using micro-chip technology.

According to her calculations, in 2010 there were more than 300 racers at the Grasslands snake pit. The estimate for 2011 is about 150 snakes.

"It was a bit of a shocker," Gardiner said, in assessing the impact the slumps have had on the snakes. "These snakes are already threatened so it was a big blow to the biggest population we know of in Canada."

She said work is now underway to see if the eastern yellow-bellied racer has established itself elsewhere.

There have been unconfirmed sightings in the Cypress Hills.

"What we're trying to do is find out if they actually are as rare as we thought," Gardiner said. "And if they're not, then maybe this blow to the population at the snake pit wasn't as significant as we thought, hopefully."

It won't be an easy task, she said, explaining that the yellow-bellied racer is an elusive creature.

"They're hard to find," she said, but added that with the concern about the numbers, researchers will be looking harder than ever for the snake.

Laura Gardiner has been studying the eastern yellow-bellied racer snake and its winter hibernation pit in the Grasslands National Park. Photo courtesy Laura GardinerTo

Wednesday, March 2, 2011

Two Snakes Surviving Agriculture

Agricultural landscapes result from converting natural ecosystems into agroecosystems and contribute to a loss of biodiversity. Species that are habitat specialists may be isolated in patches of  habitat and have reduced gene flow, subsequent loss genetic diversity, and genetic differentiation may occur within the isolated populations. Two recent papers suggest that corridors that connect the populations may keep the populations in contact, allowing genes to move from one group to another.

The Grass Snake (Natrix natrix persa). 
Taken in Ephesus, Greece. Photo Credit: 
Barbara Meister and colleagues (2010) examined the genetic structure of the amphibian-eating Grass Snakes (Natrix natrix) in remnants of pristine wetland habitat embedded in an intensively used agricultural landscape in north-western Switzerland. Using seven microsatellite markers they found no genetically distinct grass snake populations in the study area that covered about 90 km2. They hypothesized that their results implies an exchange of individuals between small remnants of original habitat. In fact, they found radio tracked female snakes in agricultural situations while they were moving to egg-laying sites. Thus, gene flow may prevent  genetic differentiation of subpopulations distributed over a relatively large area. Their study area contained canals that could act as corridors for movement despite their concentrations of agricultural chemicals. Their results suggest the Grass Snake can survive in an intensively used agricultural landscape, provided suitable patches of habitat are interconnected.

In a second study Page E. Klug and colleagues looked at genetic differences in Yellow-bellied Racer (Coluber constrictor flaviventris) populations in the highly fragmented tall grass prairies of Kansas. An estimated 4% of the original widespread prairie habitat remains. The study looked at racer populations spread out over 13,500-km of landscape in northeastern Kansas. The racer population had high allelic diversity, high heterozygosity, and was maintaining a migration-drift equilibrium. Racers exhibited restricted dispersal within 3 km, and significant isolation-by- distance occurred on broad regional scales of about 100 km. However, like the Grass Snakes there was sufficient gene flow between locations, and the authors were unable to define discrete subpopulations. In northeastern Kansas, Yellow-bellied Racer appear to be abundant and continuously distributed, suggesting the fragmented landscape is not impeding gene flow.

While these studies suggest the Grass Snake and the Yellow-bellied Racer can continue to survive in fragmented landscapes, other species may not be so lucky.

Meister, B., U. Hoffer, S. Ursenbacher, B. Baur. 2010. Spatial genetic analysis of the grass snake, Natrix natrix (Squamata: Colubridae), in an intensively used agricultural landscape. Biological Journal of the Linnean Society, 101: 51–58. doi:10.1111/j.1095-8312.2010.01474.x

Klug, P. E.. S. M. Wisely and K. A. With. 2011. Population genetic structure and landscape connectivity of the Eastern Yellowbelly Racer (Coluber constrictor flaviventris) in the contiguous tallgrass prairie of northeastern Kansas, USA. Landscape Ecology 26(2):281-294. DOI: 10.1007/s10980-010-9554-2