Persistence of Northern Pacific Rattlesnakes masks the impact of human disturbance on weight and body condition
2015
Lomas, E. | Larsen, K. W. | Bishop, C. A.
Species may remain present on developed landscapes over extended periods, suggesting viability, while in reality, populations may be indirectly affected in subtle and significant ways. We investigated indirect effects of human disturbance and habitat development on a population of the threatened Northern Pacific Rattlesnake Crotalus oreganus oreganus in British Columbia, Canada. We used mark‐recapture (n = 623 males and non‐gravid females, 2002–2011) and radio‐telemetry (n = 100 males, n = 4 non‐gravid females, 2004–2011) to examine weight, length, body condition, ecdysis and exposure risk in habitats of varying disturbance levels. Snakes in the most disturbed areas (<10 m to the nearest source of human activity or development) had lower weights and body condition, and they lost significantly more weight during the active season. Mean body condition of all snakes was stable or even increasing up to 2008 whereafter declines occurred in all categories, but particularly so for animals using disturbed habitat. Although there was some indication that ecdysis rates were affected by disturbance, we found no evidence that animals in disturbed habitat tended to be more exposed (i.e. distant from cover). Our findings indicate that there are consequences of occupying disturbed habitats, even though outward changes in behaviour or declines in density on the landscape are not detected.
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