• A reliable method for sexing giant otters (Pteronura brasiliensis) in the wild

      Groenendijk, Jessica; Hajek, Frank (2015)
      ...Here, we present a reliable method of sexing wild Giant otters of all ages and sexual status, tested with known sex individuals.
    • Cocha Cashu Biological Station

      Groenendijk, Jessica; Swamy, Varun; Aliaga, Roxana P. Arauco; Ortiz, Verónica Chávez (2019)
    • Demography of the giant otter (Pteronura brasiliensis) in Manu National Park, South-Eastern Peru: Implications for conservation

      Groenendijk, Jessica; Hajek, Frank; Johnson, Paul J.; Macdonald, David W.; Calvimontes, Jorge; Staib, Elke; Schenck, Christof (2014)
      The giant otter (Pteronura brasiliensis) is an endangered semi-aquatic carnivore of South America. We present findings on the demography of a population inhabiting the floodplain of Manu National Park, south-eastern Peru, arising from 14 annual dry season censuses over a 16 year period. The breeding system of territorial groups, including only a single breeding female with non-reproductive adult ‘helpers’, resulted in a low intrinsic rate of increase (0.03) and a slow recovery from decades of hunting for the pelt trade. This is explained by a combination of factors: (1) physiological traits such as late age at first reproduction and long generation time, (2) a high degree of reproductive skew, (3) small litters produced only once a year, and (4) a 50% mortality between den emergence and age of dispersal, as well as high mortality amongst dispersers (especially males). Female and male giant otters show similar traits with respect to average reproductive life-spans (female 5.4 yrs., male 5.2 yrs.) and average cub productivity (female 6.9, male 6.7 cubs per lifetime); the longest reproductive life spans were 11 and 13 years respectively. Individual reproductive success varied substantially and depended mainly on the duration of dominance tenure in the territory. When breeding females died, the reproductive position in the group was usually occupied by sisters or daughters (n = 11), with immigrant male partners. Male philopatry was not observed. The vulnerability of the Manu giant otter population to anthropogenic disturbance emphasises the importance of effective protection of core lake habitats in particular. Riverine forests are the most endangered ecosystem in the Department of Madre de Dios due to the concentration of gold mining, logging and agricultural activities in floodplains, highlighting the need for a giant otter habitat conservation corridor along the Madre de Dios River.
    • Effects of territory size on the reproductive success and social system of the giant otter, south-eastern Peru: Territory size and reproductive success in giant otters

      Groenendijk, Jessica; Hajek, Frank; Schenck, C.; Staib, E.; Johnson, P. J.; Macdonald, D. W. (2015)
      The link between resource abundance, dispersion and cooperative breeding in mammals has been a topic of much debate among ecologists. The giant otter social system is facultatively cooperative…. We conclude that giant otter societies are likely shaped by the spatial dispersion of lakes, and food abundance and dispersion within these rich patches.
    • Giant otters: using knowledge of life history for conservation

      Groenendijk, Jessica; Hajek, Frank; Johnson, Paul; Macdonald, David W.; Macdonald, David W.; Newman, Chris; Harrington, Lauren A. (Oxford University PressOxford, UK, 2017)
    • The Giant Otter: Giants of the Amazon

      Groenendijk, Jessica (White OwlBarnsley, UK, 2019)
      The aptly named giant otter is exceptionally well adapted to life in rivers, lakes and wetlands in tropical South America. Known in Spanish as lobo del rio or 'river wolf', it can be as long as a human is tall, and is the most social of the world's thirteen otter species. Each individual is identifiable from birth by its pale throat pattern, as unique as your fingerprint. Giant otters are top carnivores of the Amazon rainforest and have little to fear… except man.There are many reasons why scientists and tourists alike are fascinated by this charismatic species. Spend a day in the life of a close-knit giant otter family and you’ll realise why. Learn about their diet and hunting techniques, marking and denning behaviour, and breeding and cub-rearing strategies, including shared care of the youngest members. Become familiar with the complex life histories of individual otters over their 15-year lifespans. And accompany a young disperser during the trials and tribulations of a year spent looking for a mate and a home of its own.Although giant otters have few natural enemies, they became the target of the international pelt trade in the 1940s, and by the early 1970s had been hunted to the brink of extinction. Today, illegal hunting is a minor hazard. So why is the giant otter still endangered? Find out about current threats to the species and discover how a variety of conservation actions are benefiting the otters over the last decades. Then be a part of the solution by acting on the steps we can all take to help further giant otter conservation.