Effects of capturing and collaring on polar bears: findings from long-term research on the southern Beaufort Sea population

Abstract

Context The potential for research methods to affect wildlife is an increasing concern among both scientists and the public. This topic has a particular urgency for polar bears because additional research is needed to monitor and understand population responses to rapid loss of sea ice habitat. Aims This study used data collected from polar bears sampled in the Alaska portion of the southern Beaufort Sea to investigate the potential for capture to adversely affect behaviour and vital rates. We evaluated the extent to which capture, collaring and handling may influence activity and movement days to weeks post-capture, and body mass, body condition, reproduction and survival over 6 months or more. Methods We compared post-capture activity and movement rates, and relationships between prior capture history and body mass, body condition and reproductive success. We also summarised data on capture-related mortality. Key results Individual-based estimates of activity and movement rates reached near-normal levels within 2–3 days and fully normal levels within 5 days post-capture. Models of activity and movement rates among all bears had poor fit, but suggested potential for prolonged, lower-level rate reductions. Repeated captures was not related to negative effects on body condition, reproduction or cub growth or survival. Capture-related mortality was substantially reduced after 1986, when immobilisation drugs were changed, with only 3 mortalities in 2517 captures from 1987–2013. Conclusions Polar bears in the southern Beaufort Sea exhibited the greatest reductions in activity and movement rates 3.5 days post-capture. These shorter-term, post-capture effects do not appear to have translated into any long-term effects on body condition, reproduction, or cub survival. Additionally, collaring had no effect on polar bear recovery rates, body condition, reproduction or cub survival. Implications This study provides empirical evidence that current capture-based research methods do not have long-term implications, and are not contributing to observed changes in body condition, reproduction or survival in the southern Beaufort Sea. Continued refinement of capture protocols, such as the use of low-impact dart rifles and reversible drug combinations, might improve polar bear response to capture and abate short-term reductions in activity and movement post-capture.

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity

“…Accordingly, much attention has been placed on the role of summer sea ice loss in affecting Arctic ecosystems (Laidre et al, 2015;Slagstad et al, 2011). Because polar bears rely year-round on sea ice as a platform to hunt their primary prey, iceassociated seals, many studies have focused on the direct effects of decreased sea ice extent on polar bear behavior and population dynamics (Regehr, Lunn, Amstrup, & Stirling, 2007;Rode et al, 2010;Rode, Pagano, Bromaghin, 2014;Rode, Regehr, Douglas, et al, 2014;Rode et al, 2015;Whiteman et al, 2015). Our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems and that sea ice loss may have both direct and indirect effects at upper trophic levels.…”

“…Cherry, Derocher, Stirling, and Richardson (2009) documented reduced spring (i.e., March-April) foraging success evidenced by a greater frequency of fasting over the previous 7 days or more in 2005-2006 compared to 1985-1986. Furthermore, Rode, Pagano, Bromaghin, et al (2014) and Rode, Regehr, Douglas, et al (2014) documented that frequencies of fasting in the southern Beaufort Sea (SB) were much higher than those observed in the adjacent CS in recent years. These observations were concurrent with documented declines in polar bear body condition, cub survival, and population size in the SB between the 1980s and 2000s, and with maintained or improved body condition and cub survival in the CS-all during a time when both subpopulations were experiencing substantial summer sea ice loss (Rode, Regehr, Douglas, et al, 2014).…”

“…Weather data at each capture site were obtained from the North American Regional Reanalysis (Mesinger et al, 2006) using the Env-DATA portal (Dodge et al, 2013) at www.movebank.org (accessed November 2016). Sea ice characteristics were quantified within a 100-km radius around each capture location, the average net distance (plus one standard deviation) that polar bears move in 7 days during March and April, excluding the first 7 days post-capture (see Appendix S1; Rode, Pagano, Bromaghin, et al, 2014). Mean (and SD) daily sea ice concentration (%) and sea ice drift (km/day) during the week prior to capture were derived for each capture location using 25 km 9 25 km resolution grids obtained from the National Snow and Ice Data Center (see Appendix S1).…”

The seasonal energetic landscape of an apex marine carnivore, the polar bear

“…Archival loggers stopped recording between 5 October and 25 November 2014 ( = 1 November). To ensure that the data were unbiased by post‐capture recovery (Thiemann et al , Rode et al 2014 a ), we excluded data collected in April. To enable comparison among individuals, we also excluded data collected after September.…”

Injury scores and spatial responses of wolves following capture: Cable restraints versus foothold traps

“…In general, bears ( Ursus spp.) may exhibit reduced movements following capture, as indicated by polar bears ( U. maritimus ; Cattet et al , Rode et al ) and brown bears ( U. arctos ; Støen et al ), but return to normal movement rates within 2–3 days (Thiemann et al , Rode et al ). Cougars ( Puma concolor ) in southcentral New Mexico, USA, remained closer to capture locations during the first 3 days postcapture compared with ≥4 days postcapture (Logan et al ).…”