Comparative feeding strategies and kinematics in phocid seals: suction without specialized skull morphology

Abstract

Feeding kinematic studies inform our understanding of behavioral diversity and provide a framework for studying the flexibility and constraints of different prey acquisition strategies. However, little is known about the feeding behaviors used by many marine mammals. We characterized the feeding behaviors and associated kinematics of captive bearded (), harbor (), ringed () and spotted () seals through controlled feeding trials. All species primarily used a suction feeding strategy but were also observed using a biting strategy, specifically pierce feeding. Suction feeding was distinct from pierce feeding and was characterized by significantly faster feeding times, smaller gapes and gape angles, smaller gular depressions and fewer jaw motions. Most species showed higher variability in suction feeding performance than in pierce feeding, indicating that suction feeding is a behaviorally flexible strategy. Bearded seals were the only species for which there was strong correspondence between skull and dental morphology and feeding strategy, providing further support for their classification as suction feeding specialists. Harbor, ringed and spotted seals have been classified as pierce feeders based on skull and dental morphologies. Our behavioral and kinematic analyses show that suction feeding is also an important feeding strategy for these species, indicating that skull morphology alone does not capture the true diversity of feeding behaviors used by pinnipeds. The ability of all four species to use more than one feeding strategy is likely advantageous for foraging in spatially and temporally dynamic marine ecosystems that favor opportunistic predators.

Hawaiian monk seals exhibit behavioral flexibility when targeting prey of different size and shape

“…Maximum gape occurred first, followed by maximum gular depression and then finally jaw closure. This kinematic sequence matches that described for other pinnipeds (Marshall et al, 2008(Marshall et al, , 2014(Marshall et al, , 2015Kienle et al, 2018). Compared with other seal species for which comparable data exist (i.e.…”

“…Hawaiian monk seals primarily used suction feeding, regardless of prey size and shape. Their suction feeding behavior is similar to that described for other pinnipeds (Marshall et al, 2008(Marshall et al, , 2014(Marshall et al, , 2015Hocking et al, 2014;Kienle et al, 2018), showing that suction feeding in pinnipeds follows a conserved sequence of behaviors. Suction feeding was kinematically distinct from pierce feeding and characterized by shorter temporal events, such as jaw closure, maximum gape angle closing velocity, maximum gular depression and overall feeding times, as well as smaller maximum gapes and gape angles, larger maximum gular depressions and fewer jaw motions when compared with pierce feeding.…”

“…One seal was occasionally observed making repeated dorso-ventral motions of the lower jaw and gular region when using suction feeding to consume night smelt (5.88% of night smelt suction feeding trials) after prey was inside the mouth prior to swallowing. This behavior has been observed in other pinnipeds and is sometimes referred to as chewing (Hocking et al, 2014(Hocking et al, , 2015(Hocking et al, , 2016Kienle et al, 2018).…”

“…The first objective of this study was to document the feeding strategies of Hawaiian monk seals through controlled feeding trials. Previous studies have demonstrated the prevalence of suction feeding in pinnipeds, regardless of skull or dental morphology (Marshall et al, 2008(Marshall et al, , 2014(Marshall et al, , 2015Hocking et al, 2012Hocking et al, , 2014Hocking et al, , 2015Kienle et al, 2018). Based on these studies, we tested whether skull morphology corresponds with feeding strategy in Hawaiian monk seals.…”

“…The two most common pinniped feeding strategies are biting (specifically pierce feeding) and suction feeding. Pierce feeding, characterized by using the jaws and/or teeth to puncture and capture prey, is often used in combination with suction, and prey are swallowed whole with little to no processing (Marshall et al, 2008(Marshall et al, , 2014(Marshall et al, , 2015Hocking et al, 2014;Kienle et al, 2018). Suction feeding is characterized by the generation of a subambient pressure differential that draws water and prey into the mouth (Gordon, 1984;Marshall et al, 2008).…”