Jaguar mobbing by giant otter groups

Group-living in carnivores is mostly associated with cooperative hunting and anti-predator defense. Giant otters (Pteronura brasiliensis) live in monogamous and cooperative breeding groups, where mechanisms other than cooperative foraging may be driving group maintenance in the species. We herein describe three interactions between giant otters and jaguars (Panthera onca) observed in the wild, two of which involved groups of otters and one, a lone individual. In the two group instances, the otters mobbed the jaguar until it left the area. The mobbing behavior displayed in these instances likely reinforces the advantages of living in groups, reducing predation risk and promoting group cohesion, with resulting territorial and fitness benefits.     

Genetic evaluation of an otter translocation program

The translocation of individuals from onepopulation to another is a common technique inwildlife conservation. However, the outcome oftranslocation programs is not always properlyevaluated and the relative contribution ofreleased individuals to the resident populationoften remains unknown. We used mitochondrialDNA and autosomal genetic markers to evaluatethe success of a translocation program ofEurasian otters (Lutra lutra) in Sweden.The program is regarded as successful becauseof subsequent population growths. Norwegianotters used for the restocking program could begenetically differentiated from Swedish otters.The releases took place at two sites. In anarea south of the first site, where 47 otterswere released, no genetic contribution of theintroduced animals to the population could beobserved and the genetic diversity was lowerthan before the releases. At the second site,the release of seven otters led to a change ingenetic composition of the resident population.The results of this study suggest that thegrowth of the otter population after therestocking may not be as dependent on thereleases as initially suspected. The geneticeffects of the translocations appear to berestricted to areas in the immediate vicinityof the release sites.     

Mechanical properties of river otter limb bones

The determination of the bone strengths of wild animals has many potential advantages, which include the ability to estimate age of animals; monitor strengths of bones as influenced by contaminants, particularly lead; provide appropriate data for design of capture, handling, and holding equipment to minimize the possibility for bone fracture in captured animals; and measure effects of nutrition on bone strength. The objectives of of this study were to provide data on the mechanical properties of limb bones of river otters and to consider effects of age and sex on the properties. Three-point bending and shear tests were conducted on the radius, ulna, tibia, and fibula. The three-point bending tests were first conducted on the bones loaded within their elastic limit. These tests were used to evaluate the modulii of elasticity of the bones. The data on the modulii indicated that age and sex did not have significant effects on the values. The four different bones tested had approximately the same modulus of elasticity, with an average value of 14. 1 gigapascal (GPa). The shear tests were conducted on the limb bones to failure in order to determine the maximum breaking force and strength of the bones. The shear force of the radius tended to increase with age and there was a significant (P < .001) age effect. The shear force of the ulna for males was significantly (P < .002) higher than that of the females. A similar trend was observed for the fibula (P < .03). The shear strength of the radius increased with age and there was a significant (P < .005) age effect. There was also a significant (P < .001) effect of sex on shear strength of the radius; values for females were higher. There were no significant effects of sex or age found on shear strengths of the ulnae, tibia, and fibulae.     

The otter (Lutra lutra) in Tunisia

The otter is common and widespread in northern Tunisia and the Oued Medjerda effectively represents a southern limit for the species. The distribution of otters is largely coincident with dense bankside cover, provided mainly by Nerium oleander. Rivers south of the O. Medjerda offer little shelter for the animals.     

River otter and mink occupancy dynamics in riparian systems

Semi-aquatic mammals are dependent upon streams and riparian areas, which are a product of the landscapes they drain. Both local stream morphology and surrounding land use are likely to have important influences on current occupancy of semi-aquatic mammals and potentially affect future geographic distributions. We identified aspects of the riparian system and stream structure at multiple scales that relate to the presence of river otter (Lontra canadensis) and mink (Neovison vison) to better understand how changing landscapes affect occupancy dynamics of these semi-aquatic mammals and to facilitate future monitoring and management. We estimated multi-season occupancy using 103 sites sampled over 6 seasonal sampling periods in southern Illinois, USA (44,526 km²) during 2012–2014. We hypothesized river otter and mink occupancy were related to multiple aspects of landscape and local habitat attributes including land cover, water availability, human disturbance, and stream characteristics. Occupancy of river otter was predicted by large stream size, less developed area near the stream site, and proximity to areas with reintroduced or remnant populations of river otter. Mink were more likely to occupy sites with small streams and decreased water availability near the site. However, top models for both species had low weights and high uncertainty for multiple variables. Habitat-based models may not be the best predictors of occupancy for these carnivores because they are more likely to respond to prey diversity or availability, but landscape changes that decrease natural water availability and increase human disturbance to the stream at the local scale are likely to negatively affect river otter. © 2019 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

River otter population size estimation using noninvasive latrine surveys

Across much of North America, river otter (Lontra canadensis) populations were extirpated or greatly reduced by the early 20th century. More recently, reintroductions have resulted in restored populations and the recommencement of managed trapping. Perhaps the best example of these river otter reintroductions occurred in Missouri, regarded as one of the most successful carnivore recovery programs in history. However, abundance estimates for river otter populations are difficult to obtain and often contentious when used to underpin management activities. We assessed the value of latrine site monitoring as a mechanism for quantifying river otter abundance. Analyses of fecal DNA to identify individual animals may result in an improved population estimate and have been used for a variety of mammal species. We optimized laboratory protocols, redesigned existing microsatellite primers, and calculated genotyping error rates to enhance genotyping success for a large quantity of river otter scat samples. We also developed a method for molecular sexing. We then extracted DNA from 1,421 scat samples and anal sac secretions (anal jelly) collected during latrine site counts along 22–34-km stretches representing 8–77% of 8 rivers in southern Missouri in 2009. Error rates were low for the redesigned microsatellites. We obtained genotypes at 7–10 microsatellite loci for 24% of samples, observing highest success for anal jelly samples (71%) and lowest for fresh samples (collected within 1 day of defecation). We identified 63 otters (41 M, 22 F) in the 8 rivers, ranging from 2 to 14 otters per river. Analyses using program CAPWIRE resulted in population estimates similar to the minimum genotyping estimate. Density estimates averaged 0.24 otters/km. We used linear regression to develop and contrast models predicting population size based on latrine site and scat count indices, which are easily collected in the field. Population size was best predicted by a combination of scats per latrine and latrines per kilometer. Our results provide methodological approaches to guide wildlife managers seeking to initiate similar river otter fecal genotyping studies, as well as to estimate and monitor river otter population sizes. © 2011 The Wildlife Society.     

The otter (Lutra lutra L.) in Spain

In a survey of Spain during June 1981, signs of otters were found at seventy (40%) of the 176 stations investigated. Otters were mainly concentrated in the mountainous north and north-west and in the plains and mountains of the south-west. Water pollution appears to be an important limiting factor in some areas.     

Lymphosarcoma in a sea otter (Enhydra lutris)

Lymphoblastic lymphosarcoma involving the mesenteric lymph node and thymus was discovered in a 4 yr old male sea otter (Enhydra lutris). Diagnosis was based on gross and light microscopic studies. The cause of this neoplasm was not determined. This is the first case of lymphosarcoma reported in sea otters.     

The changing otter population of Britain 1700–1989

Otters Lutra lutra were persecuted increasingly in Britain for fishery protection and for sport throughout the 18th and 19th centuries. There are indications of a population recovery occurring during the 1914–1918 war with the temporary cessation of hunting and keepering. Intensive otter hunting with packs of hounds throughout the 1920s and 1930s appears to have stressed the population by altering the age structure. A catastrophic decline occurring simultaneously over England, Wales and southern Scotland, but most severe in the south-east and starting in 1957–1958, appears to have been triggered in this stressed population by a single new factor, pollution of the rivers by organochlorine insecticides. The trough in the decline may have occurred around 1977— 1979. The first signs of rivers being re-occupied by otters have been seen by the early 1980s and partial recovery seems possible with legal protection and improved water quality.     

The otter (Lutra lutra L.) in western France

In a survey of western France during October-November 1980, signs of otters were found at 46 (15%) of the 315 sites investigated. Otters were largely restricted to four areas, three of these being in the uplands (of Brittany, the Massif Central and the Pyrenees) and one in the coastal lowlands (of the Landes-Gironde). The average number of signs found per successful site was 1 6, significantly lower than for Scodand and Ireland but similar to the figure for England. The percentage of positive sites and the scattered nature of the signs in western France was also broadly comparable witJi the English situation. This is surprising since most of the factors which adversely affect otters appear to be less oppressive there dian in England. Only water pollution is noticeably more extreme and this seems to offer the best, overall explanation for the nature of the decline in the area studied.     

Foraging strategies and prey switching in the California sea otter

Summary Southern sea otters (Enhydra lutris nereis), in recovering from near extinction, are gradually extending their range to include areas from which they have been absent for more than one hundred years. This study took advantage of the otters' relatively sudden arrival in the area near Santa Cruz, California, to monitor their prey selection in the first two years of residence there. Foraging observations revealed that sea urchins (Strongly-locentrotus franciscanus) were heavily preyed upon initially, but virtually disappeared from the diet after one year of sea otter residence. The disappearance of sea urchins was accompanied by an increased use of kelp crabs (Pugettia producta) and the appearance of clams (Gari californica) in the otters' diet. Abalones (Haliotis rufescens) and cancer crabs (Cancer spp.) remained fairly stable as dietary items throughout the two year period. An electivity index was used to quantify sea otter preferences, which corresponded closely with a ranking scheme based on energy intake/unit foraging time calculated for each major prey species. As predicted by optimal foraging theory, sea otters prefer food species of high rank and replace depleted dietary items with those of next highest rank. The process of dietary switching was analyzed with respect to foraging success rates, and it appears that poor success rates, associated with predation on an increasingly rarer prey species (sea urchins), drive sea otters to hunt for different prey. Both patch selection and search image formation appear to function in this process. The potential effects on community structure and stability of predators exhibiting a preference for the most profitable prey are discussed.     

Electrocardiography of the Asian small-clawed otter (Aonyx cinerea)

For electrocardiography to be a useful diagnostic tool, it is important to establish the electrocardiographic parameters of a specific population under similar conditions of data collection. Electrocardiograms (ECGs) collected from 14 (4.10) Anoyx cinerea, chemically immobilized with a ketamine/midazolam combination, are analyzed for their mean, range, and standard deviation of parameters. A mean dosage of 10.7 mg/kg ketamine combined with 0.23 mg/kg midazolam is required for immobilization. The effects of chemical immobilization on ECG parameters were found to be minimal, with the exception of an increase in heart rate.     

Coccidioidomycosis in a California sea otter (Enhydra lutris).

A weak and emaciated California sea otter (Enhydra lutris) was found stranded on Atascadero Beach in Morro Bay, California. It died three weeks after capture. A diagnosis of coccidioidomycosis was confirmed by histology, serology and culture. This is believed to be the first reported case of this disease from the Morro Bay area of San Luis Obispo County, California as well as the first reported case in a free-ranging marine mammal.