Using Models of Social Transmission to Examine the Spread of Longline Depredation Behavior among Sperm Whales in the Gulf of Alaska

Abstract

Fishing, farming and ranching provide opportunities for predators to prey on resources concentrated by humans, a behavior termed depredation. In the Gulf of Alaska, observations of sperm whales depredating on fish caught on demersal longline gear dates back to the 1970s, with reported incidents increasing in the mid-1990s. Sperm whale depredation provides an opportunity to study the spread of a novel foraging behavior within a population. Data were collected during National Marine Fisheries Service longline surveys using demersal longline gear in waters off Alaska from 1998 to 2010. We evaluated whether observations of depredation fit predictions of social transmission by fitting the temporal and spatial spread of new observations of depredation to the Wave of Advance model. We found a significant, positive relationship between time and the distance of new observations from the diffusion center (r2 = 0.55, p-value = 0.003). The data provide circumstantial evidence for social transmission of depredation. We discuss how changes in human activities in the region (fishing methods and regulations) have created a situation in which there is spatial-temporal overlap with foraging sperm whales, likely influencing when and how the behavior spread among the population.

Harnessing learning biases is essential for applying social learning in conservation

“…There have been documented cases where social learning has been implicated in aiding the spread of conflict or problematic behaviours, such as the depredation of fishing catches by sperm whales ( Physeter macrocephalus ) (Schakner et al 2014a), crop raiding behaviours by African elephants ( Loxodonta Africana ) (Chiyo et al 2012) and spreading bears’ and dolphins’ reliance on anthropogenic foods (Mazur and Seher 2008; Donaldson et al 2012). These types of conflict can foster negative attitudes towards wildlife, can reduce support for local conservation programs and lead to persecution or culling of conflict species (Mpanduji et al 2004; Thirgood et al 2005).…”

Learning and conservation behavior: an introduction and overview

“…In elephants (Loxodonta africana), for example, network analysis of crop raiders has demonstrated that the behavior appears to be socially learned through social networks (Chiyo et al 2012). Correspondingly, social learning is believed to underlie the diffusion of depredation in sperm whales, killer whales and pilfering black bears (Whitehead 2004, Mazur & Seher 2008, Schakner et al 2014. In these cases, it is important to know both the identity of innovators (age/sex) and the pattern of diffusion.…”

How do fishing practices influence sperm whale (Physeter macrocephalus) depredation on demersal longline fisheries?

“…Both pelagic and demersal longlining are subject to depredation worldwide (Forney et al, 2011;Mesnick et al, 2006;Muñoz-Lechuga et al, 2016;Passadore et al, 2015;Rabearisoa et al, 2012;Roche et al, 2007;Straley et al, 2006;Visser, 2000). While the issue on depredation remains sporadic in some fisheries, it has spread and substantially increased in others, jeopardizing their sustainability (Powell and Wells, 2011;Schakner et al, 2014) and raising a critical need for solutions to minimize or suppress it (Hamer et al, 2012).…”

“…In both hemispheres, demersal longline fisheries are primarily depredated by adult male sperm whales whose natural foraging grounds often overlap with fishing areas (Ashford et al, 1996;Best, 1979;Mesnick et al, 2006;Whitehead, 2003). Sperm whale depredation has been reported in the North Pacific on fisheries targeting Pacific halibut (Hippoglossus stenolepis) and sablefish (Anoplopoma fimbria) (Hill et al, 1999;Peterson and Carothers, 2013;Schakner et al, 2014;Sigler et al, 2008;Straley et al, 2006), in the North Atlantic on fisheries targeting Greenland halibut (Reinhardtius hippoglossoides) (Dyb, 2006b) and in the Southern Ocean on fisheries targeting Patagonian toothfish (Dissostichus eleginoides) (Duhamel, 2003). For the latter, sperm whale depredation occurs off Chile 7 2004; Moreno et al, 2008), the Falklands/Malvinas (Goetz et al, 2011;Nolan et al, 2000), South…”