By Steve Galea
If winter doesn’t stick around longer than it should, Haliburton’s deer herds will likely enter spring in good shape.
Ministry of Northern Development, Mines and Natural Resources and Forestry (MNDMNRF) senior research scientist Brent Patterson said, “Generally speaking, it is looking like it will be a mild to moderate winter, which should have minimal impact to deer survival and recruitment.”
Dr. Patterson pointed out that snow arrived relatively late this year in central Ontario, with very little snow accumulation until mid-January. This gave deer a reprieve from challenges brought on by snow accumulations early in the season.
“Snow depth has a much greater impact on deer in winter than cold temperatures. Deep snows are detrimental to deer by reducing access to browse and forage, increasing locomotion costs, and increasing vulnerability to predators like wolves and coyotes,” he explained.
“Although cold temperatures increase the energetic demand on deer, they are able to partially compensate for this by reducing activity, having lower metabolism in winter, and choosing habitats that minimize exposure to wind. In winter, deer also maximize exposure to the midday sun and favour south facing slopes,” he added.
Patterson noted that our current snow depth is very similar to last year, with just over 40 centimetres on the ground during the first week of February.
Last year, the Percy Lake snow station had a final snow (or Snow Depth Index) accumulation of 507 centimetres in total throughout the winter. Anything under 590 centimetres is considered a mild winter. This year, that total is less than last year; the first week of February data for the Percy Lake snow station was at 175 centimetres compared to 241 centimetres at the same time last year.
“Using a predictive model based on snow depth index, a value of less than 300 centimetres in the first week of February would suggest a less than 25 per cent chance of having a severe winter outcome,” he said.
Patterson said, “A large body of research suggest that whereas cold temperatures have only a minor impact on deer survival, prolonged periods with deep snows can drastically reduce winter survival of deer. Generally, snow depths greater than 30 centimetres can measurably increase a deer’s vulnerability to predation, but snow density can be as influential as snow depth in determining impacts on deer.”
Snow depths exceeding 30 centimetres have not been experienced for long periods this winter thus far and there was even a short period when snow depth drastically decreased due to weather conditions.
Snow crusts can also affect deer in winter by inhibiting deer movement and access to available foods. Patterson said this winter several freeze/thaw cycles have created some detrimental snow crusting.
Food availability is another constant concern in winter.
“During the winter months, deer in most of Ontario subsist on a diet of low-quality food,” Patterson said. “The major food at this time of year is browse which is comprised of the woody twigs and buds of deciduous trees and shrubs, and conifer leaves from trees such as cedar and hemlock. Browse is low in protein and energy and high in fibre. Even with an unlimited food supply, deer on this winter diet will lose weight because energy demands are greater than supply as large amounts of fibre food are costly to process.”
Despite this, Patterson says deer feeding is strongly discouraged – a point the MNDMNRF has been trying to get across for years.
Feeding is risky because it causes deer to become habituated, and the wrong feed mixes can lead to digestion issues and potentially death. Additionally, a variety of feeding diseases have been documented in deer that have been fed improper diets. Habituated deer are at greater risk of causing motorized vehicle collisions as they cross roadways to get to feeding locations and Patterson notes they also pose a potentially greater threat of injury for pets and humans because feeding brings them in close proximity. Lastly, he says, congregating deer at feeding sites also means increasing the risk of them passing diseases and parasites to each other.
He said he understands the draw of deer feeding, but says the risks to the deer outweigh the benefits.
“Deer are naturally adapted to survive winter with stored fat reserves by restricting activities and reduce feeding. Artificial feeding works against these adaptations by preventing the normal seasonal reduction in metabolic rate. This could result in increased energy demands that offset the advantages of supplying artificial food. If you have deer wintering on your property, you can assist them in other ways, by creating trails (by snowshoeing or with vehicles) and by cutting browse that would otherwise be out of reach,” he said. He also says its best not to disturb deer with loud machinery, approaching too close or using snowmobiles, especially during hard winters, as this saps much needed energy from them.
Despite some of the challenges our deer are facing this winter, Patterson says this winter has, thus far, been good to them. Even predators such as wolves are generally less effective during mild winters, because deer movement and energy levels are not inhibited by deep snow and severe cold.
Though this winter has been relatively mild, Patterson cautions that winter is not over yet.
“While we are nearing the end of winter, there are still some factors that may be of concern for local deer populations. The duration of winter can impact the length of time deer spend in winter yards, thus affecting their physical condition coming into spring; this can be particularly important for pregnant females. Given the late start to the winter of 2022, this is not anticipated to be a concern; however, weather systems are becoming more variable, so spring conditions cannot be predicted. Other early spring conditions, such as timing of green up and frosts, can affect food supply and productivity too.”
And deer that have made it through a long winter can be very vulnerable to a poor or delayed spring.
Having said that, in the Haliburton area (Wildlife Management Units 54 and 56), trends in deer seen per hunter day and hunter harvest levels have been increasing since 2015 and are nearing the top end of the long-term range of values.
If the season continues as it has, this winter is not likely to change that.