• 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.
    • 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)