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Classification of the behavior of sea otters (Enhydra lutris)
Abstract and Figures
In an instantaneous sample of animal behavior, an observer must reliably recognize a behavioral unit. Previously, quantitative studies of sea otter behavior have used broadly defined activity states as behavioral units (e.g., feeding, resting, grooming, interaction, locomotion). However, an action pattern observed in an instantaneous sample may occur in the context of several different activity states. This study defines 43 discrete action patterns on the basis of form and examines natural clusters based on time sampling of focal animals. Overlap in the action patterns occurring during activity states classified by observers was determined. The possibility of using objective mathematical criteria to classify samples was examined by discriminant analysis of focal animal samples. The activity states of resting and feeding appeared sufficiently distinct to be reliably recorded during instantaneous sampling. However, there was more overlap in action patterns recorded during grooming, interaction, and locomotory activity.
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... They were also observed biting the nylon purge-valves on top of PBRs, rolling on the PBR surface, and investigating or manipulating the high-density foam floats with their paws and mouths. These are all typical sea otter behaviors observed in other contexts and in some cases with man-made objects [31,36,[38][39][40]. Otters in Moss Landing harbor have been observed to haul out on kayaks, boats, and docks (Karl Mayer, pers. ...
Background
OMEGA is an integrated aquatic system to produce biofuels, treat and recycle wastewater, capture CO2, and expand aquaculture production. This system includes floating photobioreactors (PBRs) that will cover hundreds of hectares in marine bays. To assess the interactions of marine mammals and birds with PBRs, 9 × 1.3 m flat panel and 9.5 × 0.2 m tubular PBRs were deployed in a harbor and monitored day and night from October 10, 2011 to Janurary 22, 2012 using infrared video. To observe interactions with pinnipeds, two trained sea lions (Zalophus californianus) and one trained harbor seal (Phoca vitulina richardii) were observed and directed to interact with PBRs in tanks. To determine the forces required to puncture PBR plastic and the effects of weathering, Instron measurements were made with a sea otter (Enhydra lutris) tooth and bird beaks.
Results
A total of 1,445 interactions of marine mammals and birds with PBRs were observed in the 2,424 hours of video recorded. The 95 marine mammal interactions, 94 by sea otters and one by a sea lion had average durations of three minutes (max 44 min) and represented about 1% of total recording time. The 1,350 bird interactions, primarily coots (Fulica americana) and gulls (Larus occidentalis and L. californicus) had average durations of six minutes (max. 170) and represented 5% of recording time. Interactive behaviors were characterized as passive (feeding, walking, resting, grooming, and social activity) or proactive (biting, pecking, investigating, and unspecified manipulating). Mammal interactions were predominantly proactive, whereas birds were passive. All interactions occurred primarily during the day. Ninety-six percent of otter interactions occurred in winter, whereas 73% of bird interactions in fall, correlating to their abundance in the harbor. Trained pinnipeds followed most commands to bite, drag, and haul-out onto PBRs, made no overt undirected interactions with the PBRs, but showed avoidance behavior to PBR tethers. Instron measurements indicated that sea-otter teeth and gull beaks can penetrate weathered plastic more easily than new plastic.
Conclusions
Otter and bird interactions with experimental PBRs were benign. Large-scale OMEGA systems are predicted to have both positive and negative environmental consequences.
... for a description for those behaviors without explanation, see Packard and Ribic, 1981]. The behavioral category of Locomotion and Eating included the following fifteen behaviors: Periscope, Dive, Underwater Swim, Swim, Porpoise, Side Stroke, Submerge, Sculling, Forage, Pound, Food (i.e., food handling), Eat, Chew (this occasionally included biting on or chewing the enclosure substrate), Land (climb onto terrestrial areas of the exhibit), and Walk. ...
... An ethogram was constructed based on a study by Packard and Ribic (1982), and activity budget data were collected. Activity budget categories included resting, grooming, foraging, traveling, playing, nursing, and other (i.e. ...
... The sea otter (Enhydra lutris) is the only representatives of Carnivora adapted for constant living in the aquatic environment (Barabash-Nikiforov et al., 1968). Several publications described in detail the different types of activity in these animals (feeding, grooming, traveling, interacting etc.), but provide a little information concerning their rest stages (Packard & Ribic, 1982;Ralls & Siniff, 1990;Ralls et al., 1995). Therefore, the primary aim of this study was to characterize behavioral sleep in sea otters in water and on land. ...
We observed the behavior of two captive sea otters (Enhydra lutris) in water and on land at the Utrish Marine Station of the Russian Academy of Sciences. The behavior of otters was divided into 4 distinct stages: active wakefulness (40.5–50.5% of 24 h), quiet wakefulness (21.5–30.8%), quiet sleep (23.9–35.0%), and paradoxical sleep (1.1–2.5%). During quiet sleep in water, otters floated on the back at the surface in the typical posture with both eyes closed. Paradoxical sleep was recorded both in water and on land and was characterized by jerks and twitches of the head, paws and whole body and evident muscle tone hypotonia. The main sleep period (quiet and paradoxical sleep) occurred in otters during the night when they usually slept on land. During the day otters slept only in water.
... However, the time spent grooming in and out of water increased dramatically during the first 24-48 hours after washings. Increasing time was spent at various specialized forms of in-water grooming like ''log rolling'' and ''somersaulting'' (Packard and Ribic 1982) as recovery progressed. ...
The 1989 Exxon Valdez oil spill resulted in the death of 3,000–6,000 sea otters (Enhydra lutris) from exposure to Alaska North Slope crude oil, and the cleaning and rehabilitation of hundreds. The washing and care methods developed during that experience provided standard protocols for treatment of oiled sea otters, largely still in use 20 years later. From 2004 to 2008 at the Marine Wildlife Veterinary Care and Research Center (Santa Cruz, CA, USA), we experimentally manipulated water type (salt–fresh) and temperature, and we monitored otter physiology, behavior, and thermal properties to evaluate recovery from washing in the absence of oil. We also dipped otters in canola oil, and were able to wash one otter naturally oiled with Monterey formation crude oil, using the same methods. Providing soft freshwater in recovery pools reduced recovery time substantially. Warming the freshwater appeared to offer additional benefits in some cases. Infrared thermography and subcutaneous temperature-sensitive passive integrated transponder tags were 2 new technologies that enhanced this research. The improved washing and care methods developed have the potential to reduce the time required for recovery of water repellency of sea otter pelage. © 2012 The Wildlife Society.
... We then approached the otter to within 40 m and determined its location using a global positioning system (GPS 126; Garmin International, Inc., Olathe, Kansas). Only resting and feeding behavior (Packard and Ribic 1982;Shimek and Monk 1977), which together represent 41% of the daily activity budgets for males (Finerty et al. 2009) and 57% for females with pups (R. C. Wolt, Texas A&M University, pers. comm.) were analyzed for habitat associations. ...
We investigated the habitat associations of sea otters (Enhydra lutris) during resting and feeding in an area with a predominately soft- and mixed-sediment benthos supporting infaunal prey populations in a fjord in Alaska during the summer months of 2001—2003. Water depth and benthic sediments were sampled, analyzed, and mapped throughout the bay. Sea otter locations and behavior were determined during boat surveys, and water depth, benthic sediment type, and position in the bay (peripheral compared to central) were determined for each animal location. We used logistic regression analysis to determine whether the use of habitat by sea otters was nonrandom according to these variables. Water depth was the most significant habitat association for feeding behavior, with 39% of feeding dives occurring in water 0—10 m deep. Feeding behavior was not strongly associated with sediment type. Position in the bay was the most significant habitat association for resting behavior, with the majority (63%) of otters resting in the central areas of the bay. Overall, habitat associations were nonrandom, a possible reflection of selective pressure to maximize energy intake, minimize energy expenditure, and avoid terrestrial predators.
Communication is complex and variable in long-lived and adaptable species. In such species, communication is shaped by learning, personal histories, variable social and ecological circumstances, and bonds between individuals. It is also often extremely subtle, especially in highly social species, in which individuals continually appraise and respond to the general social setting and to features of others around them: movements, activity levels, distances, postures, sounds, smells, and appearance. Much communication therefore takes place through unspecialized and undirected signals - sources of information that have not specially evolved or developed to be informative. In pinnipeds, the processes of communication are complicated further because all species communicate in both air and water. These media have different effects on sensory and motor abilities, and on physical aspects of signal transmission (Hopkins, 1987; Rogers and Cox, 1987; see Chapter 7).
Studies of sea otters in captivity began in 1932, producing important insights for conservation. Soviet (initiated in 1932) and United States (1951) studies provided information on captive otter husbandry, setting the stage for eventual large-scale translocations as tools for population restoration. Early studies also informed effective housing of animals in zoos and aquaria, with sea otters first publicly displayed in 1954. Surveys credited displayed otters in convincing the public of conservation values. After early studies, initial scientific data for captive sea otters in aquaria came from work initiated in 1956, and from dedicated research facilities beginning in 1968. Significant achievements have been made in studies of behavior, physiology, reproduction, and high-priority management issues. Larger-scale projects involving translocation and oil spill response provided extensive insights into stress reactions, water quality issues in captivity, and effects of oil spills.
Trends in abundance, distribution, and daily activities of southern sea otters, Enhydra lutris nereis, in Elkhorn Slough, a California estuary, were studied. During 66 boat-based surveys, between June and October 1994 and 1995, sea otters were counted and their location, sex, direction of movement, behavior , and degree of grizzling (an indicator of age) were recorded. During 3 night-time surveys in 1995, presence/absence patterns of sea otters were determined. An influx of sea otters into the estuary occurred between November 1994 and January 1995. Mean number of otters in 1995 (mean ± Std = 24.6 ± 5.7) was six times greater than in 1994 (mean ± Std = 4.2 ± 3.1). No significant effects of tide, or time of day, on abundance patterns were detected. Otters present in the estuary were mostly juvenile males. They were distributed along the estuary with different densities, the highest densities occurring within a resting area, where otters tended to congregate in rafts. Feeding occurred with higher frequency in areas closer to the open ocean. Clams of two different species, the Washington (Saxidornun nuttallii), and the gaper (Tresus nuttallii) were the main prey. Some individuals may use the estuary on a regular basis, since one tagged otter was observed during 58% of the surveys. The estuary was also used at night.
The behavior of sea otters (Enhydra lutris kenyoni) with dependent pups was observed between May and August of 2005–2010 in Simpson Bay, Alaska using focal follows and instantaneous sampling. Six behaviors (foraging, grooming, resting, swimming, swimming slowly and interacting) were recorded during four, 6-h time periods (dawn [05:00–11:00], day [11:00–17:00], dusk [17:00–23:00] and night [23:00–05:00]) to create a 24-h activity budget. Overall, 1190 focal follows were conducted for a total of 595 h. Females with dependent pups spent the greatest percentage of the day resting (42%), about equal percentages foraging (18%), grooming (15%), swimming (15%), swimming slowly (8%) and interacting (2%). Field Metabolic Rate (FMR) was estimated by using the oxygen consumption (ml O2 min− 1 kg− 1) for each behavior for captive otters (Yeates et al., 2007). The estimated FMR for females with a dependent pup was 12.69 MJ day− 1 with the following absolute and percentage allocations for each behavior: foraging 2.38 (19%), grooming 2.70 (21%), resting 3.42 (27%), swimming 2.64 (21%), swimming slowly 1.25 (10%) and interacting 0.3 (2%). The estimated weight specific FMR was 601 kJ day− 1 kg− 1, similar to that reported for territorial males in the same area. The sea otter population in Simpson Bay has been stable for at least the last 12 years. It would follow then that the time spent foraging might be similar to other areas where the population is stable, but this is not the case. In Simpson Bay, the time spent foraging is more similar to areas that have been recently occupied. The relatively small amount of time spent foraging may indicate that geographic differences (structure of the near-shore community: substrate, water depth, kelp canopy, prey assemblage, and competitors) may play a greater role in determining the amount of time spent foraging than population status.
During the period 24 July through 21 September 1974 sea otter (Enhydra lutris) activity was sampled along a 5.5 km stretch of coastline in Monterey County, California. Sixty-five one hour samples covering a 15 hour day were completed during the study period. Sea otter behavior was classed as resting, foraging, interacting, grooming, or swimming. There were two modes of foraging activity, at 0700 and at 1700 hours. Preliminary observations suggest a third mode of foraging activity at 2400 hours. Principal otter activities were resting and foraging. The sample data also revealed the relative importance of various sectors within the study area. Male animals appeared to move to female areas to forage.
Enhydra lutris at Amchitka Island spent 55% of daylight hours foraging; there were distinct early morning and late afternoon peaks in foraging activity; and fish made up over 60% of their overall diet by volume. The more recently established populations at Attu Island and off the coast of Oregon are far below equilibrium density. At both Attu and in Oregon, sea otters spent 17% of daylight hours foraging; there was no peak in foraging activity; and herbivorous macroinvertebrates made up their entire diet. Subsequent to overexploitation of sea otters, uncontrolled populations of herbivorous sea urchins greatly reduced or eliminated sublittoral kelp assemblages. In areas only recently reoccupied by otters, sea urchins are abundant and easily accessible as prey. Otters in these areas invest relatively little effort in foraging, and distribute that effort uniformly throughout the day. Where otters are abundant sea urchins are scarce, in turn promoting the growth of kelp beds and an associated fish fauna. Consequently otters at Amchitka invest more time in pursuit of more elusive prey (fish), and distribute that effort disproportionally toward morning and evening to correspond with availability of kelp bed fishes. -from AuthorsEnhydra lutris Amchitka Island Attu Island Oregon
The main purpose of this paper is to establish a bridgehead between contemporary ethology and some recent work in the philosophy of mind. Ethologists categorize behaviour according to its form, its function and its causation, but have not always been aware of the conceptual problems arising from the employment of several different conceptual schemes in one science. Philosophers of mind have recently discussed in detail the difference between thinking of human behaviour as action and thinking of it as movement, and I argue that this distinction is in some ways analogous to the distinction between behaviour categorized by function and by form. Wherever more than one conceptual scheme is employed in a science there is a pressure to run together concepts taken from the different schemes, and I show that such conceptual confusion in ethology can lead to obscurity, misrepresentation of experimental results, and the construction of unfruitful theories.
Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.