Counting on deer counts
Island deer won’t be counted by aerial survey in 2010, but their numbers are on the rise.
Determining deer counts can be a difficult and expensiveendeavour. This year’s numbers at Mashomack show increases in deerpopulations. But why track deer counts at all? That’s the questionthat arose following the Deer and Tick Committee’s February 17decision to discontinue one particularly costly method, the aerialflyover. At the same meeting, Cornell entomologist Dan Gilrein gavethe board an update on 4-poster program finances.
DEER POPULATION RISES
The committee voted unanimously not to order an aerial flyoverfor the purpose of tracking deer populations this season. Thetechnique has drawn criticism in the past because of itsinaccuracy. A faulty flyover in February of 2009 detected only 131deer, far fewer than counts on the ground. The aerial contractor,VisionAir of Boise, Idaho, did not charge the town for the $8,000cost of that survey.
Committee member Mike Scheibel, a wildlife biologist, called theaerial flyovers an unnecessary expense. He described alternatemethods of doing deer counts, including spotlighting, in which anobserver drives along a prescribed route, counts the number of deerhe sees, and uses that figure to estimate the number of deer over alarger area. This technique is cheap, very easy to do and providesa fairly accurate index of deer numbers, he said.
Three survey routes are conducted in Mashomack in December andthen again in February – most of the deer are harvested during theJanuary shotgun season. Mr. Scheibel said that for the previousthree to four years, there have been 80 to 100 deer per square milein December, which drops to about 14 deer per square mile inFebruary.
February spotlight counts this year indicate an increase in thenumber of deer in Mashomack, approximately 25 per square mile.”That’s a significant difference from what I’ve been seeing in thepast three or four years, Mr. Scheibel told the board.
Another method of tracking deer populations involves recordingthe size of deer harvests. In Mashomack, Mr. Scheibel said, hekeeps track of the number of hunters and how long they hunted, afigure he termed “hunter effort. He can use this figure inrelationship to the harvest size to compare deer numbers from yearto year. A greater harvest with the same hunter effort from oneyear to the next is indicative of a larger deer density.
Deer harvests reflect the spotlight count trend. About 150 deerwere harvested in Mashomack this January, compared to about 100 inthe previous three to four years with similar hunter efforts. “Thattells me that the density has gone up, said Mr. Scheibel.
The board also receives deer population data from CornellCooperative Extension, although once the 4-posters program iscomplete this source will no longer be available.
Committee member Abigail Field mentioned, “At some point we’dlike to get to the larger question: what is the purpose of doingdeer counts at this time, due to the well-establishedoverpopulation?
Mr. Scheibel said that deer numbers have managementimplications. Because of this year’s increased numbers, heconsidered extending the nuisance hunt in Mashomack, which hasn’tbeen done in previous years. But he noted that in order to managepopulations, “I don’t really need a specific number of deer¦ simply saying that there’s too many – that’s reallyall I need to know. But unless the counts indicate a need for anincrease or decrease in hunting, he said, he has no real use fordeer surveys.
FINANCES
Cornell entomologist Dan Gilrein reported that the 4-posterprogram will require, at “the barest possible minimum, anadditional $160,000 to finish the program for 2010 and another$53,000 for the beginning of 2011 to finish analyzing data and tocompile a final report. This report would be available in April tomid-May of 2011, he said.
The costs could increase, though, if the cost of certain Cornellservices or that of permethrin sampling increases. Dr. Gilrein saidto expect a maximum price tag of $240,000 to $250,000 for thecompletion of the study.