GPS Radio Collars Tracking Deer for Next 5 Years

By Lisa Kane This article also appears in the April issue of the North Woods Sporting Journal How many of you apply for an Any Deer Permit each year? These much sought-after permit allocations are based, in part, on the Maine Department of Inland Fisheries and Wildlife (MDFIW’s) estimates of the previous winter’s deer mortality, previous season’s actual hunter harvests and biological information collected during each hunting season on harvested deer. Another part of the equation is called the Winter Severity Index, or WSI. Regional wildlife biologists gather weather data weekly from 28 stations statewide to record temperature (via continuous automated data logging), snow depth and deer sinking depth. The data is applied to estimate how hard the winters are on the overall deer population, and extrapolate winter deer mortality. All of these factors, plugged into a mathematical formula, can directly influence the number of Any Deer permits issued within each Wildlife Management District (WMD). In use since 1950s, Maine’s deer allocation system has worked very successfully; however, with a changing climate, changing landscapes, and perhaps, missing data for the 2 extremes of our winter weather – the very mild and the very severe - it was time for the WSI system to be re-evaluated. Kyle Ravana, the lead MDIFW deer biologist, recently initiated a 5-yr study to conduct deer population monitoring using GPS satellite collar technology to track survival and mortality trends in Maine’s antlerless deer – i.e. does and fawns. The Goals of the project are to: 1) Reevaluate the correlation between WSI and WMR for white-tailed deer 2) Assess seasonal survival rates for the adult female (≥1.5 years) and fawn segments of the population 3) Assess cause-specific mortality of our adult female and fawn populations 4) Reassess the current winter severity index and try to identify a new, and more simplistic metric WMD 17 in central Maine was chosen as the initial study area. With approximately 20 deer per square mile and a good variation of winter severities, habitats range from hard and soft wood stands, logging operations, agricultural lands; with some urban forest on the fringes of small towns and cities like Newport, Bangor and Skowhegan. Beginning in the winter of 2014-15, 52 deer were captured and 18 collared. This year, in the winter of 2015-16, there have been 115 captures and 31 collars attached, with 45 deer transmitting data at the time of this article. Data from each collar is transmitted twice daily directly to Ravana’s computer. He can see at any time where each collared deer is on the landscape. If a deer goes down and doesn’t move for 4 hours, staff track directly to it to assess cause of death. The good news is there has not been a lot of deer mortality since the project began. One starved, one succumbed to predation, one deer was poached in St. Albans (a case still unsolved), and most recently, one deer was hit by a car. So how do you initially catch a deer? ‘Clover traps’, designed specifically for capturing deer for telemetry studies, were first designed in 1956. The first 30 traps were constructed by a contract welder and MDIFW staff; and as they were put into use, modified to better suit MDIFW’s specific needs. An additional 15 traps were added to the project in 2015. These traps have been shown to decrease the possibility of any accidental deer injuries or deaths. After first receiving landowner permission, the traps are placed in areas of high deer activity, or in known deer yards (deer wintering areas (DWAs)). They are baited with wildlife grain or natural browse, like cedar. Once set, the traps are checked daily by 6 MDIFW contractors. If a deer is captured, the trap is literally collapsed around it, and the animal is pinned down and accessed through the door at the front of the trap. The deer immediately has a hood placed over its head to calm it, the collar is bolted on and activated, a numbered ear tag applied and it’s released – all within about 3 minutes. The deer is then immediately ‘on the air’. How long do the collars last? With only 2 transmissions a day, as opposed to some studies where transmission is continuous, these collars are supposed to last 4-5 years without a battery change. To a lesser extent, two other methods of capture have also been used, a rocket net and a drop net, both over bait. Each method has been very successful, but requires that staff be there to activate the nets. Also, because the deer must be extracted from the entanglement of the nets, they must be tranquilized - which can be more risky for the animals. While deer biologists would like to get the full fleet of 60 collars on deer and transmitting to get as robust a sample as possible, all trapping will cease by mid-April to avoid unnecessary stresses on does entering their 3^rd trimester of pregnancy; and will resume next winter. As collared deer die, others will be trapped to take their place until 2019. And the study area may be expanded to other WMDs, particularly to those up north. There have been a variety of non-target species captured, including snowshoe hare, turkeys, crows, coons and squirrels. Interestingly, there has been a handful– 15 – of recaptured deer to date. The temptation of good grub must be too hard to resist! This project is funded primarily by the Maine Outdoor Heritage Fund; additionally, the Legislature appropriated extra funds to support the addition of more deer traps and radio collars. Potential changes to the Any-Deer Permit system will not take place until the study is completed and data thoroughly analyzed.