Our team of researchers recently discovered an innovative and novel behavior our population of Common bottlenose dolphins were exhibiting throughout the day. As part of our commitment to further understanding dolphin cognition and behavior (and disseminating our discoveries to the larger scientific community), our research team recently published a peer-reviewed scientific article on this fascinating behavior!
Fence Fishing: The Use of Algae by Bottlenose Dolphins to Attract Fish
Holli C. Eskelinen1,2,3, Jill L. Richardson1,2,3, and Kelley A. Winship4
1Dolphins Plus Marine Mammal Responder, 31 Corinne Place, Key Largo, Florida 33037
Email: holli@dolphinsplus.com
2Dolphins Plus, 101900 Overseas Hwy, Key Largo, Florida 33037
3Rosenstiel School for Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149
4National Marine Mammal Foundation, 2240 Shelter Island Dr. San Diego CA, 92106
Unique foraging strategies have been thoroughly documented in free-ranging common bottlenose dolphins (Tursiops truncatus). Still, descriptions of novel foraging behaviors exhibited by captive dolphins in natural seawater habitats are limited. An innovative foraging strategy was documented 32 times, involving one adult and four sub-adults manipulating various macroalgal species to interact with and lure fish into the lagoons, termed the fence feeding behavior. Individuals held small and large pieces of algae, manipulating the algae with their mouths, shaking it along the fence, spitting water at the algae to alter its position in the water column, or threading it through the fence opening (Figure 1). However, consuming the fish may not have been the objective of each bout, particularly given the low rate of fish capture noted in the recordings. Instead, the process of selecting algae and luring the fish was likely reinforcing to the animals, such that they continued to practice the behavior even when the catch rate was low. Future research should clarify the purpose and function of the behavior, whether foraging and/or enrichment/play and how the behavior is acquired and transmitted.
Figure 1. The two algal species utilized predominantly in the fence fishing behavior (N = 31): a) red week (Hypnea cervicornis) and b) sea lettuce (Ulva spp.).
Innovation observed during foraging may be influenced by the availability and ease of acquiring other resources, predation risk, social variables (e.g., cooperation), and the ability to perform alternate behaviors (Dewar, 2004; Reader, 2007) and costly behaviors, such as play and exploration (De Oliveria et al., 2003; Moller & Garamszegi, 2012). Kummer and Goodall (1985) theorized that the rate of innovation may reflect the relative surplus of time in managed care, as captive animals do not practice predator avoidance or the need to access resources for sustenance (i.e., they are provided food by their caretakers). Additionally, increased and sustained access to the animals provides opportunities to observe behaviors that may not be practiced or cannot be viewed in a wild setting. Although the study subjects were provided with fish as part of their daily care regimen, fence fishing represented an optional, relatively low-cost foraging strategy.
While the same fish species were available free-swimming in the dolphin lagoon, the use of algae to entice large schools of fish, rather than chasing them individually, was more energetically efficient. However, consuming the fish may not have been the objective of each bout, particularly given the low rate of fish consumption noted in the recordings. Rather, the process of selecting algae and attracting the fish was likely reinforcing to the animals, or cognitively stimulating, such that they continued to practice the behavior even when the catch rate was low. Continued assessments of external and internal drivers may lend insight into the purpose and evolution of this novel behavior and further elucidate how the behavior was adopted and practiced within the population, including whether for the purpose of consumption and/or enrichment/play.
Dewar, G. (2004). Social and asocial cues about new food: Cue reliability influences intake in rats. Learning and Behavior, 32, 82–89.
De Oliveira, C. R., Ruiz-Miranda, C. R., Kleiman, D. G., & Beck, B. B. (2003). Play behavior in juvenile golden lion tamarins (Callitrichidae: Primates): Organization in relation to costs. Ethology, 109, 593612.
Kummer, H., & Goodall, J. (1985). Conditions of innovative behaviour in primates. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 308, 203214.
Moller, A. P., & Garamszegi, L. Z. (2012). Between individual variation in risk-taking behavior and its life history consequences. Behavioral Ecology, 23, 843853.
Reader, S. (2007). Environmentally invoked innovation and cognition. Behavioral and Brain Sciences, 30(4), 420-421. doi:10.1017/S0140525X07002518