Lay abstract
Both Northern Rockhopper penguins and Southern Rockhopper penguins are threatened with extinction. Their numbers are declining due to loss of habitat and effects of man. Since 1973 Edinburgh Zoo has housed 84 Rockhoppers, which it has, encourage to breed as an insurance policy for the wild population. Unfortunately this has had limited success. Currently they house 18 northern rockhoppers.
Zoo records pose a rich resource for identifying causes of reproductive failure. This study aims to review these and compare them with studies done in the wild to make suggestions to help rockhoppers reproduce. Data was reviewed using organisational trees and analysed using simple statistics.
Four original wild females produced chicks, which went on to rear their own chicks to adulthood. This leads to concerns regarding the gene pool size. 44% of females do not lay eggs, those that do have 70% infertility. 49% of hatched chicks reach sexual maturity. 81% of neonatal deaths occur in the first month. Neonatal post-mortem reports were inconclusive, not giving precise reasons for chick death, and need more investigations.
Females and males are overweight at breeding season compared to wild living birds. This may reduce fertility therefore weight loss is advised. A higher proportion of eggs hatch to wild-born mothers than to captive born mothers. This maybe because wild mothers weighed less since they ate less in captivity or, their more aggressive personalities provided an outlet so stress did not affect their fertility. Both 1st and 2nd laid eggs hatch in equal numbers therefore should be treated with the same care. The current average age of females is over 21 years and so seniority may affect fertility.
Many limitations are present regarding the extent of conclusions drawn, however areas in which the reproductive process may fail have been identified and areas requiring further study highlighted.
Key words: Southern, rockhopper, Northern rockhopper, Infertility, neonatal death, overweight
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