Infektionsabwehr und lymphatischer Rachenring

Foraging behaviours used by two female Australian fur seals (Arctocephalus pusillus doriferus) were documented during controlled feeding trials. During these trials the seals were presented with prey either free-floating in open water or concealed within a mobile ball or a static box feeding device. When targeting free-floating prey both subjects primarily used raptorial biting in combination with suction, which was used to draw prey to within range of the teeth. When targeting prey concealed within either the mobile or static feeding device, the seals were able to use suction to draw out prey items that could not be reached by biting. Suction was followed by lateral water expulsion, where water drawn into the mouth along with the prey item was purged via the sides of the mouth. Vibrissae were used to explore the surface of the feeding devices, especially when locating the openings in which the prey items had been hidden. The mobile ball device was also manipulated by pushing it with the muzzle to knock out concealed prey, which was not possible when using the static feeding device. To knock prey out of this static device one seal used targeted bubble blowing, where a focused stream of bubbles was blown out of the nose into the openings in the device. Once captured in the jaws, prey items were manipulated and re-oriented using further mouth movements or chews so that they could be swallowed head first. While most items were swallowed whole underwater, some were instead taken to the surface and held in the teeth, while being vigorously shaken to break them into smaller pieces before swallowing. The behavioural flexibility displayed by Australian fur seals likely assists in capturing and consuming the extremely wide range of prey types that are targeted in the wild, during both benthic and epipelagic foraging

Mobile and Static enrichment devices.

<p>a) Mobile ball and rope enrichment device: fish are placed into the ball, which must then be manipulated by the seal in order to knock out the hidden prey items. b) Static box enrichment device: fish are hidden in the recessed tubes on the front surface of the device. Because the box device is static against the wall it cannot be manipulated to knock out prey items. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124615#pone.0124615.s005" target="_blank">S1 Video</a> for footage of the main behaviours used by the seals when interacting with these devices.</p

Summary of the experimental design used and total time of observation.

<p>Summary of the experimental design used and total time of observation.</p

Ethogram and operational definitions for Australian fur seal behaviour during the experimental sessions carried out in this study.

<p>Behaviours recorded include all major behavioural states observed during these trials, but do not constitute a complete list of behaviours displayed by Australian fur seals in captivity. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124615#pone.0124615.s005" target="_blank">S1 Video</a> for footage of some of these behaviour states.</p><p>Ethogram and operational definitions for Australian fur seal behaviour during the experimental sessions carried out in this study.</p

Summary of behaviours displayed during feeding trials.

<p>Mean duration (min) of behaviour states performed by Bay (a) and Tarwin (b) during each control and enrichment treatment. Similar behaviour states are grouped to show time spent performing: enrichment-related behaviours, pattern swimming, random swimming or any other behaviour state. Operational definitions for behaviour states are outlined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124615#pone.0124615.t002" target="_blank">Table 2</a>.</p

Experimental subjects.

<p>Experimental subjects.</p

Suction used to draw a prey item into the oral cavity filmed at 50 frames/second.

<p>a) prey item held loosely between the lips, b) prey item sucked into the oral cavity as the jaws opened to maximum gape, the arrow indicates the direction of prey movement towards the mouth, c) mouth closes and water is expelled via the lateral sides of the mouth, although this is difficult to see in cloudy water. Prey capture event performed by Bay (ARKS# A70598), a female Australian fur seal (<i>Arctocephalus pusillus doriferus</i>). Time displayed as hours:minutes:seconds:frames. For the footage see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112521#pone.0112521.s001" target="_blank">Video S1</a>.</p

Suction used to draw prey out of the static box device filmed at 25 frames/second.

<p>a) prey item was found by carefully looking into each recessed tube, b) mouth was positioned over the opening using eyes and whiskers, c) suction generated by widening the gape and retracting tongue and hyoid, d) jaws closed to grip prey with anterior teeth, while performing lateral water expulsion where seawater drawn into mouth during suction was expelled via sides of the mouth (arrows indicate cloud of turbid water being expelled), e-f) pull prey out of device while holding it with the anterior teeth before performing further manipulation and swallowing. Prey capture event performed by Tarwin (ARKS# 980419), a female Australian fur seal (<i>Arctocephalus pusillus doriferus</i>). Time displayed as hours:minutes:seconds:frames. For the footage see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112521#pone.0112521.s001" target="_blank">Video S1</a>.</p

Object manipulation and suction used to draw prey from the mobile ball device filmed at 25 frames/second.

<p>a) ball was carefully manipulated using the muzzle, while looking through the hole in its side for concealed prey, b) when a prey item is seen near the opening the seal moved its mouth over the hole before pushing the ball forward, while also generating suction to draw out the prey item, c) water expulsion visible as it is expelled via the sides of the mouth following suction (arrows indicate cloud of turbid water being expelled), d) once protruding from the hole the prey item was gripped using the anterior teeth before being pulled out and consumed. Prey capture event performed by Bay (ARKS# A70598), a female Australian fur seal (<i>Arctocephalus pusillus doriferus</i>). Time displayed as hours:minutes:seconds:frames. For the footage see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112521#pone.0112521.s001" target="_blank">Video S1</a>.</p

Summary of kinematic variables.

<p>Values are means ± s.e.m.</p><p>Summary of kinematic variables.</p