Giant Otter Science
I realise they do not strictly qualify as nature writing, but these papers are the culmination of 16 years of collaborative field research, financed by the Frankfurt Zoological Society, plus almost the same number of years (or so it seemed) of blood, sweat, and tears (read data analysis, write-up, and publication), so I felt bound to include them. My fascination with this endangered species has never waned. Giant otters started me off on my conservation career, and the rainforest experiences I have accumulated while studying them feed much of my creative writing, so I owe them a special debt of gratitude. For more information, try Friends of the Giant Otter on Facebook.
Biology and Conservation of Musteloids
Chapter 22. Giant otters: using knowledge of life history for conservation
Jessica Groenendijk, Frank Hajek, Paul J. Johnson, David W. Macdonald. (2017). In: Biology and Conservation of Musteloids. Edited by David W. Macdonald, Chris Newman, and Lauren Harrington, Oxford University Press. Available to order, published in October 2017.
Description
The editors of this book have used their combined 90 years of experience working on the behaviour and ecology of wild musteloids to draw together a unique network of the world's most successful and knowledgeable experts. The book begins with nine review chapters covering hot topics in musteloid biology including evolution, disease, social communication, and management. These are followed by twenty extensive case studies providing a range of comprehensive geographic and taxonomic coverage. The final chapter synthesises what has been discussed in the book, and reflects on the different and diverse conservation needs of musteloids and the wealth of conservation lessons they offer.
Biology and Conservation of Musteloids provides a conceptual framework for future research and applied conservation management that is suitable for graduate level students as well as professional researchers in musteloid and carnivore ecology and conservation biology. It will also be of relevance and use to conservationists and wildlife managers.
Journal of Zoology
Effects of territory size on the reproductive success and social system of the giant otter, south-eastern Peru.
Groenendijk, J., Hajek, F., Schenck, C., Staib, E., Johnson, P. J. and Macdonald, D. W. (2015). Journal of Zoology, 296: 153–160. doi: 10.1111/jzo.12231
Abstract
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. Extended families inhabit home ranges where only a dominant pair breeds, and other family members assist with cub defence and food provision. But this system can be affected by local ecology. In the floodplain of the Manu River, in Manu National Park, Peru, oxbow lakes are patchily distributed and form the resource-rich cores, or territories, of giant otter family home ranges. We present data from a long-term study at this site, linking territory size variability to the composition of resident giant otter groups and their reproductive success. Territory size predicts group structure; both the size of groups and the number of post-emergence cubs are positively correlated to the total lake area within the group territory. Territories with small lake areas (likely to be poor territories) often support only a pair, and the pair may not breed successfully every year. Cubs are more likely to survive in years when more non-breeding adults are present at the time of emergence. However, there may be a negative effect on survival where more non-breeding adults are present in the subsequent year. Finally, cubs produced in larger territories are more likely to disperse and breed successfully away from the natal territory. We conclude that giant otter societies are likely shaped by the spatial dispersion of lakes, and food abundance and dispersion within these rich patches.
Plos One
Demography of the Giant Otter (Pteronura brasiliensis) in Manu National Park, South-Eastern Peru: Implications for Conservation.
Groenendijk J, Hajek F, Johnson PJ, Macdonald DW, Calvimontes J, Staib E, et al. (2014). PLoS ONE 9(8): e106202. doi:10.1371/journal.pone.0106202
Abstract
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 lifespans (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.
