Fluctuating Asymmetry as an Indicator of Environmental Stress From Off-Highway Vehicles

Marking moose calves with an ear-tag-mounted radio- transmitter was associated with an increased mortality rate
among calves. We do not know the reason for this elevated mortality among radiomarked calves, but it is possible that the transmitter somehow affected calf behavior or the calf-
female relationship (Swenson et al. 1999b). Without a control group of unmarked calves, we would have over- estimated the predation rate by brown bears and total calf mortality rate by 68% and 69%, respectively. However, corresponding studies on other cervids have not found
Swenson et al. * Brown Bear Predation on Moose Calves 1995
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elevated mortality rates due to marking calves with radio- transmitters (Linnell et al. 1995).
Our results showed reproductive compensation in moose females following loss of calves. This has also been reported in Alaskan moose by Testa and Adams (1998) and Keech et
al. (2000), who proposed the apparent mechanism: the body condition of moose females in fall is correlated positively with pregnancy rates and calving rates, and females with greater rump fat thickness in spring give birth to more twins. Rearing calves is costly; female moose accompanied by a calf in fall had less rump fat, a lower pregnancy rate, and
smaller embryos. Therefore, lower calf survival may result in
subsequent higher reproductive rates (Testa 1998). This seems to be a general phenomenon. Managers should expect partial compensation through higher reproduction the year after a moose female has lost her calves, especially when this
happens early in the calves’ lives.

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