According to Penn State researchers, deer fawns are most likely to survive if born in farmland rather than woodlands. The results of the study, which was published on May 1, are based on four different study areas in Pennsylvania combined with fawn-survival estimates from published data in 16 states and 29 deer populations.
We've read through the study’s findings and put together a short list of highlights and quick data points. To read more, check out the full article posted to PSU.edu.
The Cruel Truth
Throughout the white-tailed deer's range only about half of all fawns live to see their first birthday — most are killed by predators.
A Predator’s Kitchen Is Not in the Cornfield?
Adjunct professor of wildlife ecology Duane Diefenbach, whose research group in Penn State’s College of Agricultural Sciences conducted the work, noted that it is the first large-scale study to link predation of fawns to habitat characteristics.
Agriculture Is Life Support
The estimated average fawn survival to six months of age was about 41 percent in contiguous forest landscapes with no agriculture. For every 10 percent increase in land area in agriculture, fawn survival increased by almost 5 percent.
What Makes Farmland Better for Fawns?
It seems that predators are not as efficient at finding fawns in grasslands or croplands. And, in a camera-trapping research project researchers have in progress now, they are seeing fewer predators in farmland habitat than in forests.
Coyotes Verses Bobcats Verses Black Bears: Who Does It Best?
"Coyote predation was a greater source of mortality than black bear or bobcat predation, especially in the southeastern U.S," said Diefenbach, who is the leader of the Pennsylvania Cooperative Fish and Wildlife Research Unit at Penn State. "But black bears accounted for similar, or greater, proportions of mortality compared to coyotes in several studies we reviewed."
Deer Density and Starvation
Natural sources of mortality such as starvation and abandonment occurred in similar proportions across all landscapes, and human causes — classified as death by agricultural machinery and vehicle collisions — were the smallest source of mortality. The study failed to detect any relationship between fawn survival and deer density.
Mama Knows Best
The findings likely explain some of the movement researchers see with female deer, when a few leave forested areas and go to farmland habitat to have fawns. The animals seem to sense they have greater success rearing fawns in agricultural areas.
Final Takeaway
Diefenbach believes this research has important wildlife management implications across the country. The meta-analysis of the study indicates efforts to alter fawn survival to increase overall deer numbers will be challenging. Although predation is the largest source of mortality and occurred at the greatest rates, predator control efforts are difficult and often unsuccessful.
"Managers looking to influence fawn mortality by increasing habitat diversity and maintaining a landscape structure with a mix of agriculture and forest may observe less fawn predation," he said. "However, reduced antlerless harvests may be more effective at achieving deer population objectives than attempts to manipulate the factors that influence fawn mortality."
