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Providing evidence to improve practice

Individual study: Captive-bred large whites Pieris brassicae are larger, lay more eggs and have smaller wings than wild individuals; experiments at the University of Oxford, Oxfordshire, England

Published source details

Lewis O.T. & Thomas C.D. (2001) Adaptations to captivity in the butterfly Pieris brassicae (L.) and the implications for ex situ conservation. Journal of Insect Conservation, 5, 55-63

Summary

Breeding butterflies in captivity for conservation carries a risk that captive butterflies will develop traits not well suited to their natural environment, such as larger bodies and shorter wings. This study compared traits of large whites Pieris brassicae bred in captivity with those of a recently wild-caught population, at the University of Oxford, Oxfordshire, UK.

Eggs were collected from two sources – a ‘captive’ group, bred in captivity for more than 25 years (100-150 generations) at Horticulture Research International, Warwickshire, UK, and a ‘wild’ group collected from the field at Bridgend, Glamorgan, South Wales. The captive group originated from butterflies caught in southern England.

Butterflies were reared from these eggs in groups, fed on fresh cabbage leaves.

The following measurements were taken: egg-laying by 15 mated females from each group confined with males in flight cages for 16 days; number of mature eggs and mass of ovaries in unmated females after one, two, four and six days; total adult body mass, mass of thorax, wing area and aspect ratio (wingspan2/wing area) in freshly emerged males and females (the number of individuals measured for size is not specified).

Captive females laid more eggs than wild females. They laid on 11 of the 16 days, up to 90 eggs per female on average, compared to less than 10 eggs/female on only three of the 16 days, for wild butterflies.

There was no difference between captive and wild groups in the number of mature eggs produced by unmated females (66 captive, 44 wild females measured). Captive females had heavier ovaries (average 7.9 mg) than wild-caught females (average 5.8 mg) two days after emergence (15 captive, 11 wild females measured), but not after four or six days (23 and 17 females measured).
 
Captive butterflies were heavier than wild butterflies (average mass around 1.9 g, compared to 1.8-1.85 g for wild butterflies). There was no difference in thorax mass.
 
Captive females had smaller wings and both sexes had broader, shorter wings (lower aspect ratio) than wild butterflies (wing area was not compared for males).
 
The authors recommend keeping butterflies in relatively large enclosures similar to wild environments for captive breeding, to reduce these changes.
 
 
Note: If using or referring to this published study, please read and quote the original paper, the abstract of which can be viewed at: http://www.springerlink.com/content/h36m326545300x28/