Energetic implications of disturbance caused by petroleum exploration to woodland caribou

Abstract

Woodland caribou (Rangifer tarandus caribou) in Alberta are classified as endangered and apparently have declined. Disturbance from petroleum exploration has been implicated as a possible cause, so we constructed a simple model to estimate the energy costs of multiple encounters with disturbance (i.e., loud noise). Our objective was to estimate if woodland caribou in northeastern Alberta have been exposed to enough disturbance from 1988 to 1993 to cause winter mass loss to exceed either (i) 15% autumn mass or (ii) 20% autumn mass. A single disturbance event costs caribou 3.46-5.81 MJ. Caribou would have to encounter (i) 20-34 (mean = 27) disturbance events to lose >15% mass over winter and (ii) 41-137 (mean = 89) events to lose >20% mass. There were five occasions from 1988 to 1993 (i.e., in a particular caribou distribution zone and winter) when the encounter rate (number of potential encounters per square kilometre) exceeded a level expected to result in caribou losing more than the estimated mean 15% autumn mass. There were four occasions when the encounter rate exceeded the lower limit expected to cause >20% mass loss and one occasion when it approached the mean rate expected to cause >20% mass loss. Modelling the cumulative influence of disturbances demonstrates an effect on individual energy loss during winter at certain exploration intensities. It is the first attempt at estimating the consequences of petroleum exploration for wildlife in northeastern Alberta and provides important information for future research and land-use management.Résumé : En Alberta, la population du Caribou des bois (Rangifer tarandus caribou) est réputée en voie de disparition et elle est effectivement en déclin; les perturbations occasionnées par les opérations pétrolières y contribuent probablement. Nous avons construit un modèle mathématique simple qui permet d'estimer les coûts énergetiques associés aux instances multiples de telles perturbations (notamment le bruit intense). Nous avions pour objéctif d'estimer si la population a subi suffisamment de perturbations entre 1988 et 1993 pour occasionner une perte de masse en hiver supérieure (i) à 15% de la masse à l'automne ou (ii) à 20% de la masse à l'automne. Une seule perturbation coûte à un caribou de 3,46 à 5,81 MJ. Un caribou doit donc être soumis à (i) entre 20 et 34 (moyenne = 27) perturbations pour perdre plus de 15% de sa masse en hiver et (ii) à entre 41 et 137 (moyenne = 89) perturbations pour en perdre plus de 20%. Entre 1988 et 1993, il y a eu cinq circonstances (i.e., dans une zone de répartition particulière et au cours d'une saison précise) où le taux des perturbations (nombre de perturbations potentielles par kilomètre carré) a été plus élevé que le nombre théorique susceptible d'engendrer une perte moyenne de masse de plus de 15% en hiver. Il y a eu quatre circonstances où ce taux a dépassé le seuil inférieur susceptible de provoquer une perte de masse de plus de 20% et une seule circonstance où il s'est approché du taux moyen relié à une perte de masse de plu...

Heading for the hills? Evaluating spatial distribution of woodland caribou in response to a growing anthropogenic disturbance footprint

“…For example, shifting ranges away from anthropogenic disturbance could alleviate some of the proximate threats faced by these herds (predation and stress associated with disturbance; Bradshaw et al. ; Hebblewhite et al. ), but the effectiveness of this strategy in contributing to the long‐term persistence of caribou likely depends on the availability and quality of alternative ranges (Saher and Schmiegelow ; Sawyer et al.…”

“…By limiting caribou movement rates and altering the future use of habitat, annual fluctuations in climate could limit the effectiveness of the moving‐away strategy for mountain caribou and may also change the viability of alternative ranges for caribou, especially as food availability and energetic costs in high elevation habitat are dependent on snow depth (Bradshaw et al. ; Johnson et al. ; Kinley et al.…”

Effects of natural resource development on the terrestrial biodiversity of Canadian boreal forests

“…The most endangered populations in the western boreal zone have ranges that are affected substantially by oil and gas developments (Sorensen et al 2008;Athabasca Landscape Team 2009;Environment Canada 2011). Habitat loss (Bergerud 1974), noise (Bradshaw et al , 1998Seip et al 2007), roads (Dyer et al 2001), total human activity (Dyer et al 2001), increased predation (Sorensen et al 2008), and seismic lines (James and Stuart-Smith 2000; Athabasca Landscape Team 2009) associated with energy production all have negative effects on woodland caribou habitat, survival, and (or) productivity. These studies together indicate that oil and gas developments cause habitat loss for caribou through multiple mechanisms.…”

The Effect of Human Activities and Their Associated Noise on Ungulate Behavior

“…An increase in vigilance may be costly if it results in a decrease in maintenance activities such as foraging [21], [22], and displacement or flight may expend valuable amounts of energy [23]–[25]. Thus, noise can affect habitat selection, foraging patterns, and overall energy budgets [26], [27], with potential population-level effects. However, noise may not have lasting negative effects if animals habituate to the disturbance, that is exhibit reduced responsiveness over time after repeated exposure without consequence [28]; e.g., [5], [29]–[31].…”