Identification of prey captures in Australian Fur Seals (Arctocephalus pusillus doriferus) using head-mounted accelerometers: field validation with animal-borne video cameras

This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey captures (APC), and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were unable to distinguish among prey types (fish, cephalopod, stingray) or between successful captures and unsuccessful capture attempts. Mean detection rate (true positive rate) on individual animals in the testing subset ranged from 67-100%, and mean detection on the testing subset averaged across 4 animals ranged from 82-97%. Mean False positive (FP) rate ranged from 15-67% individually in the testing subset, and 26-59% averaged across 4 animals. Surge and sway had significantly greater detection rates, but also conversely greater FP rates compared to heave. Video data also indicated that some head movements recorded by the accelerometers were unrelated to APC and that a peak in acceleration variance did not always equate to an individual prey item. The results of the present study indicate that head-mounted accelerometers provide a complementary tool for investigating foraging behaviour in pinnipeds, but that detection and FP correction factors need to be applied for reliable field application

Use of anthropogenic sea floor structures by Australian fur seals: potential positive ecological impacts of marine industrial development?

Human-induced changes to habitats can have deleterious effects on many species that occupy them. However, some species can adapt and even benefit from such modifications. Artificial reefs have long been used to provide habitat for invertebrate communities and promote local fish populations. With the increasing demand for energy resources within ocean systems, there has been an expansion of infrastructure in near-shore benthic environments which function as de facto artificial reefs. Little is known of their use by marine mammals. In this study, the influence of anthropogenic sea floor structures (pipelines, cable routes, wells and shipwrecks) on the foraging locations of 36 adult female Australian fur seals (Arctocephalus pusillus doriferus) was investigated. For 9 (25%) of the individuals, distance to anthropogenic sea floor structures was the most important factor in determining the location of intensive foraging activity. Whereas the influence of anthropogenic sea floor structures on foraging locations was not related to age and mass, it was positively related to flipper length/standard length (a factor which can affect manoeuvrability). A total of 26 (72%) individuals tracked with GPS were recorded spending time in the vicinity of structures (from <1% to >75% of the foraging trip duration) with pipelines and cable routes being the most frequented. No relationships were found between the amount of time spent frequenting anthropogenic structures and individual characteristics. More than a third (35%) of animals foraging near anthropogenic sea floor structures visited more than one type of structure. These results further highlight potentially beneficial ecological outcomes of marine industrial development

Movements of monk seals relative to ecological depth zones in the lower Northwestern Hawaiian Islands

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Quantifying free-roaming domestic cat predation using animal-borne video cameras

Domestic cats (Felis catus) are efficient and abundant non-native predators. Predation by domestic cats remains a topic of considerable social and scientific debate and warrants attention using improved methods. Predation is likely a function of cat behavior, opportunity to hunt, and local habitat. Previous predation studies relied on homeowner reports of wildlife captures from prey returns to the household and other indirect means. We investigated hunting of wildlife by owned, free-roaming cats in a suburban area of the southeastern USA. Specific research goals included: (1) quantifying the frequency of cat interactions with native wildlife, (2) identifying common prey species of suburban cats, and (3) examining predictors of outdoor behavior. We monitored 55 cats during a 1-year period (November 2010–October 2011) using KittyCam video cameras. Participating cats wore a video camera for 7–10 total days and all outdoor activity was recorded for analysis. We collected an average of 38 h of footage from each project cat. Forty-four percent of free-roaming cats hunted wildlife, of which reptiles, mammals, and invertebrates constituted the majority of prey. Successful hunting cats captured an average of 2.4 prey items during 7 days of roaming, with Carolina anoles (Anolis carolinensis) being the most common prey species. Most wildlife captures (85%) occurred during the warm season (March–November in the southern USA). Twenty-three percent of cat prey items were returned to households; 49% of items were left at the site of capture, and 28% were consumed. Our results suggest that previous studies of pet cat predation on wildlife using owner surveys significantly underestimated capture rates of hunting cats

Loggerhead Turtles (<i>Caretta caretta</i>) Use Vision to Forage on Gelatinous Prey in Mid-Water

<div><p>Identifying characteristics of foraging activity is fundamental to understanding an animals’ lifestyle and foraging ecology. Despite its importance, monitoring the foraging activities of marine animals is difficult because direct observation is rarely possible. In this study, we use an animal-borne imaging system and three-dimensional data logger simultaneously to observe the foraging behaviour of large juvenile and adult sized loggerhead turtles (<i>Caretta caretta</i>) in their natural environment. Video recordings showed that the turtles foraged on gelatinous prey while swimming in mid-water (i.e., defined as epipelagic water column deeper than 1 m in this study). By linking video and 3D data, we found that mid-water foraging events share the common feature of a marked deceleration phase associated with the capture and handling of the sluggish prey. Analysis of high-resolution 3D movements during mid-water foraging events, including presumptive events extracted from 3D data using deceleration in swim speed as a proxy for foraging (detection rate = 0.67), showed that turtles swam straight toward prey in 171 events (i.e., turning point absent) but made a single turn toward the prey an average of 5.7±6.0 m before reaching the prey in 229 events (i.e., turning point present). Foraging events with a turning point tended to occur during the daytime, suggesting that turtles primarily used visual cues to locate prey. In addition, an incident of a turtle encountering a plastic bag while swimming in mid-water was recorded. The fact that the turtle’s movements while approaching the plastic bag were analogous to those of a true foraging event, having a turning point and deceleration phase, also support the use of vision in mid-water foraging. Our study shows that integrated video and high-resolution 3D data analysis provides unique opportunities to understand foraging behaviours in the context of the sensory ecology involved in prey location.</p></div

Summary of deployments.

*<p>L0711 was used for the study twice because it was recaptured by a set net after the first deployment.</p>**<p>Abbreviations were used for logger type: 3D (W1000-3MPD3GT), C₁ (Crittercam Gen 5.5) and C₂ (Crittercam Gen. 5.7).</p

An encounter with a plastic bag.

<p><b>A</b>. A plastic bag encountered by turtle L0708 while swimming in mid-water at a depth of 24.3 m. <b>B</b>. Horizontal movements made by the turtle while approaching the plastic bag. The dashed arrow shows the direction of the movement. The position where the turtle reached the plastic bag and the turning point are indicated by blue and red arrows, respectively. The black arrow indicates where the plastic bag appeared in the clip (Fig. 4A) which was 0.4 m before the turtle reached the plastic bag.</p

Characteristics of mid-water foraging events recorded by video data.

*<p>Mean swim speed of each phase was calculated from speed data without applying any smoothing procedures.</p

Comparison of approach distance during daytime and night-time events.

<p>Comparison of approach distance during daytime and night-time events.</p

Horizontal movements during mid-water foraging events.

<p>Examples of foraging events recorded at 05∶04 on 20 August 2007 at a depth of 21.3 m (<b>A</b>), at 07∶15 on 3 September 2009 at a depth of 18.3 m (<b>B</b>), and at 05∶21 on 20 August 2007 at a depth of 18.3 m (<b>C</b>). A dashed arrow indicates the direction of movement for each path. Red and blue arrows indicate the turning point and the bite point. Note that there was no turning point in C.</p