IUCN/SSC Otter Specialist Group Bulletin
©IUCN/SCC Otter Specialist Group
Volume 42 Issue 1 (March 2025)
Abstracts
Monitoring Otter Abundance in uKhahlamba Drakensberg Park, South Africa
Pages 53 - 62 (Article)
Sonja Krüger
uKhahlamba Drakensberg Park is one of the largest and most important inland freshwater protected areas in South Africa for both the African clawless otter Aonyx capensis and spotted-necked otter Hydrictis maculicollis. The relative abundance of both species was estimated by recording the number of spraint sites at four localities on three major rivers in the park for six consecutive years at the same time each year. Findings were compared with previous surveys done during the 1970s and 1990s at all four localities, and in 2010 at one of them, using the same methods. Otter spraint site abundance in this study differed significantly between species and study sites but not between years, with spotted-necked otter being more abundant than African clawless otter. There was a significant difference in otter spraint site abundance between study periods, and the relationship between species and study periods. The results indicated that the park’s otter population had not declined significantly in the past 30 years. An observed difference was that more sign of spotted-necked otter was found in the current study, whereas in previous studies the sign of African clawless otter was more abundant. The park thus continues to contribute to otter conservation in the country, particularly that of the spotted-necked otter. Further studies are required to determine the drivers of the annual fluctuations in the number of sign, and the substantial increase in spotted-necked otter sign in the park in recent years.
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Intergroup Conflict and Myiasis-Induced Mortality in a Giant Otter from the Brazilian Pantanal: Implications for Population Conservation
Pages 63 - 70 (Report)
Greice Z. Gonchoroski, Abigail Martin, Gabriela Raphael, Livia A. Rodrigues, Mariana M Furtado, Guilherme M. Mourão, and Caroline Leuchtenberger
Agonistic encounters, characterized by confrontations and conflicts, have been documented across various animal taxa. Intraspecific conflicts are more common in socially structured populations such as the giant otter (Pteronura brasiliensis), a gregarious and territorial species. Here, we present the evolution of injuries resulting from a territorial dispute between two giant otter groups during the dry season in a disturbed touristic area in the Brazilian Pantanal. The injuries of a dominant male showed an unfavorable progression of a myiasis leading to the individual's death and implications for the social dynamics of the group and for conservation of the population.
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North American River Otter (Lontra canadensis) Predation on Brown Pelicans (Pelecanus occidentalis) at Abbotts Lagoon, Point Reyes National Seashore, California, USA
Pages 71 - 84 (Report)
Terence Carroll and Megan Isadore
North American river otters (Lontra canadensis) are opportunistic predators whose diet preferences may have ecosystem effects. In Northern California, USA, river otters are a recovering species, and their diet commonly includes waterbirds. Beginning in 2018, we observed and documented river otter predation on Brown pelicans (Pelecanus occidentalis), a novel prey choice for river otters, at a coastal lagoon. To investigate this emerging predator-prey relationship, in 2023 we conducted repeated surveys from June through November to identify and document the carcasses of Brown pelicans that had been predated by river otters. In 19 surveys, we found 73 carcasses. Carcass counts on individual surveys ranged from 0 to 11, with a mean of 3.84 carcasses per survey. Comparing carcass counts to weekly average pelican abundance, as reported by eBird, we found a moderate correlation between the two. Based on the location of the largest grouping of pelicans we observed on each survey, we found no evidence that, in the aggregate, pelicans altered their pattern of use of the lagoon in response to predation. Spatial analysis of carcass distribution revealed no significant clustering, suggesting that predation occurred across different areas of the lagoon. This study sheds light on the dietary choices of river otters, and also highlights important ecological questions. Persistence of this predator-prey relationship may influence nutrient cycles, as pelican carcasses are a nutrient subsidy for local scavengers. Our findings underscore the need for further study into the long-term effects of river otter predation on pelican populations, and on broader ecosystem dynamics in coastal environments.
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