| Summary: | This study was undertaken to determine if mallards (Anas platyrhynchos) use kin
recognition during mate choice as a means to achieve optimal outbreeding and to examine the
consequences of inbreeding on breeding success. Mallards hatched from eggs collected in the
wild were raised and bred to produce ducklings that were either inbred (parents were sibs) or
outbred (parents not sibs). Ducklings were raised in isolated subfamily groups so that when
sexually mature, they could be tested for mate preference among 4 choices: 1) a sib that was a
brood mate, 2) a sib that the subject had not seen before, 3) a first cousin not previously seen,
4) an unrelated individual not previously seen. The initial preference test was inconclusive. In
the second mate choice test when the subject and the four choice objects were allowed to
interact for 22 hours, neither inbred, outbred females, nor outbred males showed any consistent
preference. Inbred males, however, significantly avoided the familiar sister. The results
provided no strong support for mallards using kin recognition to achieve optimal outbreeding,
but rather suggested kin recognition as a mechanism for severe inbreeding avoidance. Optimal
outbreeding in mallards may be achieved via other mechanisms such as female natal site fidelity.
Comparison of mate compatibility between pairs of siblings (inbred matings) and pairs of
unrelated individuals (outbred matings) indicated that males paired with a sister performed
significantly less pre-copulatory head-pumping and were significantly more aggressive to their
mates than males paired with an unrelated female. Breeding success was examined by
comparing the laying characteristics and fertility of these pairs and comparing the
morphological measurements of the resulting ducklings. While fertility was not affected, there was a 50% reduction in hatchability of eggs from inbred matings. Inbred ducklings also had
significantly lighter body mass and shorter extremities at days 15, 30 and 45 post-hatch
compared to outbred ducklings. Although inbreeding depression was clearly evident after only
one generation of full-sib mating, an occasional brother-sister mating may not seriously reduce
the fitness of the population as a whole. === Land and Food Systems, Faculty of === Graduate
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