The following piece was written by OAS Communications Coordinator AnnaKathryn Kruger for the Snapshot Wisconsin newsletter. To subscribe to the newsletter, visit this link. 

Wisconsin is renowned for being home to a well-established population of white-tailed deer. They are an undeniably important part of Wisconsin’s forests and farmland and are the animal that appears most frequently on Snapshot Wisconsin trail cameras. Since its inception in 2016 the project has accrued a massive supply of deer photos. This vital cache of information offers researchers the opportunity to make population-level observations about things like movement and activity patterns, and how these change with the seasons.

Out of a sample of 1.4 million Snapshot Wisconsin trail camera photos of deer, antlerless deer take the lead at 63%. The remaining 37% comprises antlered (13%), adult unknown (15%) and fawns (8%).

In their ongoing analyses of these photos, scientists at the Wisconsin DNR have noted that deer show strong crepuscular patterns near both the summer and winter solstices. The word crepuscular refers to the interim between night and day, or both dawn and dusk. Deer are more active closer to sunrise and sunset than they are at any other time of day across any season. In winter, there is an observable preference toward sunset – most likely because afternoon is the warmest time of the day, and therefore the best for foraging. The opposite goes for the longer days in summer, when deer seem to prefer sunrise, as it is cooler and foraging at that time is less energetically expensive.

During the summer, antlered deer are the most likely to stick to this crepuscular pattern. On the other hand, antlerless deer and fawns are a little more unpredictable. Fawns are generally more active throughout the day, as are antlerless deer, though to a lesser extent. Antlerless deer are also more active through the night. Assuming that most antlerless deer are does, their deviation from the crepuscular pattern can be attributed to their need to move to and from spots where they drop their fawns in the time following birth. Despite their penchant for daytime activity, after the first 12 weeks fawns begin to mirror the activity of their mothers, gradually falling into the recognizable crepuscular pattern.

As for winter, both antlered and antlerless deer are seen to be most active at sunset. At this point, fawns are indistinguishable from does and are therefore not differentiated from the rest of the population in the analysis. During the winter, antlered deer are more active during the night and less active during the day than antlerless. Predictably, the annual rut drives a significant uptick in activity for male deer in late October, a pattern familiar to Wisconsin drivers who may be liable to encounter deer more frequently around the same time.

Snapshot Wisconsin’s growing cache of deer photos sheds light on deer activity as it varies through the seasons and even day-to-day. Recognizing these patterns bolsters our knowledge of how deer interact with and move through the landscape. These photos are also used to investigate population dynamics and determine fawn-to-doe ratios to better track the growth of the herd. Such a plentiful supply of information on an important species like deer is of great value to our researchers, whose analyses are a critical component of wildlife management decision-making at the Wisconsin DNR.