Mule deer die with full stomachs
This winter took a bite out of Montana's deer numbers and other ungulate, or hoofed populations, especially in the eastern half of the state. Montana Fish, Wildlife & Parks biologists are responding to calls about dead or dying deer, and April has yet to bring relief.
"April can be the harshest time of year for deer," said Julie Cunningham, FWP wildlife biologist in Bozeman. "Deer and other ungulates survive winter by layering on fat through summer and early fall and then they slowly burn those reserves throughout the winter."
If the winter is particularly long or harsh, as this one was, many animals come close to burning up those energy stores with no suitable forage to replace them. The result may be a female that is unable to sustain a pregnancy, or full out starvation.
A deer on the verge of starvation that gets into a rancher's haystack, or eats grain offered by a concerned landowner, may actually be more likely to succumb than those that continue to forage on dry grass and stubble.
"Deer on a winter diet of woody vegetation need time for their systems to adjust to a high carbohydrate diet, for example, grain or corn," said Kent Laudon, an FWP wildlife biologist in Kalispell with research experience in Idaho studying the winter survival of deer.
Deer have four stomach compartments. Before food passes from the rumen, or first compartment, it must be broken down by a finely-tuned combination of microorganisms and enzymes. In a sudden shift to a new high-carbohydrate diet, the microorganisms in the gut may not adapt fast enough to digest the material. In that case, the rumen remains filled with undigested matter that may quickly ferment, producing excessive bacteria and lactic acid. The resulting change in pH destroys the normally occurring digestive organisms. Depending on several factors, including the amount of food consumed, the result ranges from serious indigestion to death.
"Artificially feeding deer leads to a variety of issues—none of them good for the deer," Laudon said.
In other cases, a deer that is starving can commonly also "starve out" the microorganisms in its gut that would normally digest food. When the animal does find food its system is too weakened to make use of it.
Marrow of a starving deer
"In studies of the bone marrow of starving deer the marrow is a deep red, gelatinous material rather than the white, solid look of normal marrow," Laudon said. "The marrow is an indicator of late-stage starvation because it is the last fat to be used. An animal with gelatinous bone marrow is in the final stages of starvation."
There are things people can do to help deer and other ungulate species during a harsh winter. Most important is to avoid disturbing wildlife. At this point in the season, the stress of being pursued, photographed, roused by a snowmobile or 4-wheeler, or chased by a dog can make the difference between whether some animals live or die. They are literally down to their last few days of reserve energy.
For those who live in the transition zone between an urban and a wild area, avoid feeding deer and keep dogs under control and close to home.
For more information on living with wildlife, see our Living With Wildlife Tips.
Montana restrictions and regulations prohibit anyone from providing supplemental feed attractants to game animals by: purposely or knowingly attracting bears with supplemental feed attractants…or purposely or knowingly providing supplemental feed attractants in a manner that results in an artificial concentration of game animals that may potentially contribute to the transmission of disease or that constitutes a threat to public safety…"Supplemental feed attractant" means any food, garbage, or other attractant for game animals.