Feeding kinematics, suction and hydraulic jetting capabilities in bearded seals (Erignathus barbatus)

Abstract

SUMMARYFeeding kinematics, suction and hydraulic jetting capabilities of bearded seals (Erignathus barbatus) were characterized during controlled feeding trials. Feeding trials were conducted both on land and in water, and allowed a choice between suction and biting, but food was also presented that could be ingested by suction alone. Four feeding phases, preparatory, jaw opening, hyoid depression and jaw closing were observed; the mean feeding cycle duration was 0.54±0.22·s, regardless of feeding mode (P>0.05). Subjects feeding on land used biting and suction 89.3% and 10.7% of the time, respectively. Subjects feeding in water used suction and hydraulic jetting 96.3% and 3.7% of the time, respectively. No biting behavior was observed underwater. Suction feeding was characterized by a small gape (2.7±0.85·cm), small gape angle (24.4±8.13°), pursing of the rostral lips to form a circular aperture, and pursing of the lateral lips to occlude lateral gape. Biting was characterized by large gape (7.3±2.2·cm), large gape angle (41.7±15.2°), and lip curling to expose the teeth. An excavation behavior in which suction and hydraulic jetting were alternated was used to extract food from recessed wells. The maximum subambient and suprambient pressures recorded were 91.2 and 53.4·kPa, respectively. The inclusion of suction data for phocids broadens the principle that suction feeding kinematics is conserved among aquatic vertebrates. Furthermore, bearded seals support predictions that mouth size, fluid flow speed, and elusiveness of prey consumed are among a suite of traits that determine the specific nature of suction feeding among species.

Comparative feeding kinematics and performance of odontocetes: belugas, Pacific white-sided dolphins and long-finned pilot whales

“…Additionally, belugas adducted the hyoid (and presumably the tongue) just prior to the onset of feeding events (Phase I), which probably functions to remove residual water from the oral cavity and maximize the volume change at the onset of hyolingual depression. Similar behaviors reported in other suction feeding specialists (Lauder, 1980b;Marshall et al, 2008) support this hypothesis. Results from previous mammalian suction performance studies indicate that faster hyolingual and jaw kinematics are associated with suction (Kastelein et al, 1997;Werth, 2000a;Bloodworth and Marshall, 2005;Marshall et al, 2008).…”

“…Similar behaviors reported in other suction feeding specialists (Lauder, 1980b;Marshall et al, 2008) support this hypothesis. Results from previous mammalian suction performance studies indicate that faster hyolingual and jaw kinematics are associated with suction (Kastelein et al, 1997;Werth, 2000a;Bloodworth and Marshall, 2005;Marshall et al, 2008). This relationship is also prominent among teleosts, with an extreme case represented by sygnathids (de Lussanet and Muller, 2007;Van Wassenbergh et al, 2008;Van Wassenbergh et al, 2009).…”

“…Behavioral adaptations that allow belugas to create a pursed circular aperture are clearly integral to prey capture and suction capability in belugas. This was evidenced by suction pressures similar to other mammals capable of some of the greatest subambient pressures known among vertebrates (walrus: 91.4-118.8kPa, bearded seal: 91.2kPa) (Fay, 1982;Kastelein et al, 1994;Marshall et al, 2008). In conjunction with the contribution of orofacial morphology, it is possible that hyolingual adduction and hydraulic jetting observed at the onset of the feeding event may also enhance suction generation by enhancing intraoral volume displacement.…”

“…This pattern may be especially beneficial to obligate bidirectional flow suction feeders, including odontocetes. Lateral gape occlusion is a common behavioral adaptation of suction feeders, including odontocetes and pinnipeds (Werth, 2000a;Bloodworth and Marshall, 2005;Marshall et al, 2008). The nonkinetic mammalian skull constrains lateral occlusion but this function can be taken on by the oral lips in a behavior analogous to lateral gape occlusion via labial cartilages of elasmobranchs (e.g.…”

“…Suction feeding is characterized by rapid buccal volume expansion that generates a pressure gradient and a flow of water and prey into the mouth (Muller et al, 1982;Wainwright and Day, 2007). While suction generation has been best studied among more basal vertebrates, suction performance data for secondarily aquatic vertebrates (such as marine mammals) are limited to only a few pinniped (Fay, 1982;Kastelein et al, 1994;Marshall et al, 2008) and cetacean taxa (Kastelein et al, 1997;Werth, 2000a;Bloodworth and Marshall, 2005;Werth, 2006b).…”