Abstract

Though currently listed as a vulnerable species by the World Conservation Union (IUCN) African penguins are common display animals in North American zoos and aquariums. At present 43 American Zoo and Aquarium (AZA) accredited institutions, maintaining over 700 African penguins, participate in a species survival plan (SSP) for this species. A survey of these facilities found that seven institutions, (holding 23 percent of the captive North American population) maintain their birds in saltwater habitats, while the remaining institutions employ freshwater habitats. Seventy percent of all the freshwater-maintained birds received salt-supplemented diets. Currently, 14 institutions maintain their birds in freshwater without salt supplementation. These institutions have reported no associated health issues. By assaying and comparing plasma electrolyte concentrations, this ten-month controlled study objectively addresses the question of whether plasma electrolytes of salt-supplemented African penguins maintained in freshwater differ from those of similarly maintained non-supplemented conspecifics.

Thirty-eight captive African penguins from four facilities were utilized in this study. Facilities in the United States included Mystic Aquarium, Mystic, CT; Seneca Park Zoo, Rochester, NY; and, Potawatomi Zoo, South Bend, IN (Table 1). Additionally, electrolyte data were obtained from free-ranging birds in South Africa (SA) (n=20) and long-term residents (n=13) and rehabilitated oil spill birds (n=47) at the Southern African Foundation for the Conservation of Coastal Birds (SANCCOB) facility. Data were checked for normality using the Shapiro-Wilk test and found to have a normal distribution. Analysis of variance (ANOVA) and repeated measures ANOVA were used to compare means between groups as well as between time periods.

Comparison of electrolytes of salt-supplemented verses unsupplemented birds at Mystic Aquarium showed that there were no differences between the two groups. The temporal pattern of plasma electrolyte values over the study duration was the same for the two groups with some statistically significant differences among the six sampling periods. These findings suggest that supplementation has no effect on serum electrolytes and that there may be a natural seasonal variation in serum electrolyte levels in this species, a finding we will explore further. In addition, there were no differences in electrolyte concentrations for birds housed at Mystic Aquarium, Potawatomi Zoo and Seneca Park Zoo at the start of the study. Similarly, home pen birds at SANCCOB and wild African penguins had equivalent electrolyte levels. The oil-contaminated birds however, had significantly lower sodium and higher potassium concentrations. Comparisons between U.S. birds and healthy SA birds showed no significant difference in plasma sodium or chloride concentrations, but the SA birds exhibited significantly higher potassium concentrations. Potassium level differences likely result from different sample handling techniques.

This study supports the hypothesis that African penguins maintained in freshwater exhibits, on a herring-, smelt-, and capelin-based diet, do not require salt supplementation.

Table 1. Summary of salt supplement by habitat type and diet.

Acknowledgements

We wish to thank Dr. Nola Parsons at SANCCOB for facilitating collection of samples and analysis of samples in South Africa, the animal care staffs at Mystic Aquarium, Potawatomi Zoo and Seneca Park Zoo for their support with animal care and handling during blood collection; Gayle Sirpenski and Amy DelMonaco for hematology analysis, Pfizer Analytic Laboratory for plasma chemistry analysis; and Dr. Todd Schmitt for assistance during the early period of the study.