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The Science, Ethics, and Philosophy of Tooth Extractions from Live-captured White-tailed Deer: a response to Festa-Bianchet et al. (2002)

Additional Data and Analysis on Mortality, Weights, and Reproduction


To address the notion of canine removal affecting weight dynamics, reproduction, and survival, I retrospectively examined the data for sufficient samples of deer with intact canines to compare to deer with a canine extracted, henceforth referred to as "intact" and "extracted" deer. Because I removed a canine from all yearling and adult deer (>41 kg at capture), intact deer samples came from deer captured and radiocollared as fawns and monitored until death or radiocollar expiration (typically at the end of 4 years of age). Because I captured deer during late winter, yearlings were not available for comparison until 2 years old. Thus, my only comparative survival data are from 2- through 4-year-old females. Small samples further necessitated combining ages. Furthermore, I could not examine effects on weight dynamics and reproduction because so few deer were recaptured and weighed a second time, and I could not consistently verify fawn production. Thus, I was able to analyze only survival in a manner conforming to Festa-Bianchet et al.'s (2002) requirement for acceptance of tooth extraction.

In concluding that there are harmful consequences from canine extraction, Festa-Bianchet et al. (2002) further claimed that such effects may be subtle and may manifest themselves most in old deer. I also lack sufficient data to dispel this claim with a solid analysis. Few deer survived beyond 10 years, let alone survived to be recaptured and weighed. Lacking such a sample of old intact deer to make the appropriate comparison, I nonetheless present weight data from 4 females >10 years old, recaptured > 1 year after their first capture and tooth extraction. Similarly, I detail the minimum fawn production by a female closely monitored from 4 through 14 years old. Finally, I present fawn production data as documentation of reproduction in extracted deer > 10 years old. I offer these descriptive findings as minimum evidence where only speculation existed previously. Perhaps they will provide additional grist for thought, discussion, and ideas for future research.

Mortality
My mortality analysis (Micromort; Heisey and Fuller 1985) of 2-4-year-olds found that 41 intact females surviving 21,754 deer-days and sustaining nine natural mortalities (7 wolves, 2 unknown) had a mean annual mortality of 0.14 (95% CI= 0.05-0.22). Eighty-five extracted females survived 41,253 deer-days and had 12 natural mortalities (9 wolves, 3 unknown), resulting in a mean annual mortality of 0.10 (95%CI=0.05-0.15). Thus, there was no significant difference in mortality rates between the two samples (Z=0.779, P=0.40).

Weights
The winter recaptures and weighing of four females >10 years old enabled comparisons of their pre- and post-tooth-extraction weights >1 year after their first captures. A 9.8- and 10.8-year-old, respectively, weighed 4 kg and 1.4 kg more at their recaptures 354 and 365 days later when snow conditions were identical to those at the time of the first capture. An 11.8-year-old was 11 kg heavier 7 years after her first capture when she was 4.8 years old. She probably reached her maximum weight between 5.0-7.5 years old (Mech and McRoberts 1990), so some of this gain is no doubt due to growth and to the fact that I recaptured her on 27 January, midway in the seasonal weight decline experienced by all northern deer (DelGiudice et al. 1992). However, as of the date of recapture, 50-67-cm snow depths had been present for 12 weeks, creating a snow index twice that at the initial capture. There can be no doubt that prior to recapture, she had lost substantial weight, burning fat reserves as she waded through deep snow.

I recaptured and weighed a 14.5-year-old female six times between 4.8 and 12.8 years. She weighed 2-11 kg more at each recapture and was heaviest (81 kg) at 10.8 years old, 2 years after I extracted her second canine to test the accuracy of cementum aging. She probably had good fat stores at the time because I recaptured her in early winter, and the winter was extremely mild. However, even in a moderately severe winter when 7 years old, she was still a heavy 79 kg when captured in late winter near the bottom of the annual weight cycle. From a sample of 277 females, she weighed the most of only four other extracted females weighing >72 kg.

Fawn production
I also documented minimum fawn production by eight extracted females aged 10-14 years old, including the aforementioned heaviest female. This female produced at least one fawn each year for 6 years and 2 fawns each year for 2 years between 5 and 13 years old (6-year-old production was unknown). She produced at least five fawns after her second canine extraction at 8.8 years old.

The other seven 10-14-year-old females produced at least 11 fawns during 8 summers, 9 in the first, 1 in the second, and 1 in the third summer after their tooth extractions. In addition to these, a female with a canine extracted at 1.9 years old contained twin fetuses when hit by a vehicle just prior to parturition at 13.9 years old.

Age effects
Festa-Bianchet et al. (2002) argued that their proposed subtle effects of tooth extraction would be manifest most in old age, implying that youthful vigor and growth would mask such effects. Thus I will not present my recapture and fawn production data from many younger deer but rather cite a previous analysis (Nelson and Mech 1990) that found no significant differences in weights and fawn production between younger (2-9 years old) and older (>10 years old) deer despite the fact that the younger sample included intact deer and the older sample only extracted deer where the effect should have been most obvious.


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