EFFECT OF TRANSATLANTIC TRANSPORT ON REPRODUCTION OF AGOUTI AND NONAGOUTI DEER MICE, PEROMYSCUS-MANICULATUS

In conjunction with establishing colonies of deer mice in the UK, effe cts of transportation on reproduction in agouti (A) and nonagouti (a) deer mice were assessed. Adults were shipped via ground courier and ai r freight from Northampton, Massachusetts, USA to Sutton Bonington, Le icestershire, England in February and June. Deer mice were paired upon arrival in Sutton Bonington, whereas matched controls were paired in the original colonies at shipping. To assess reproduction, the followi ng variables were monitored for 110 days for all 96 pairs: number of p airs producing Litters, time from pairing to birth, interlitter interv al, Litter size at birth, and litter size at weaning. Generally, shipp ing suppressed litter production and delayed its timing, but had less effect on litter size. Overall, 32 of 48 control pairs (67%) produced 69 litters compared with 37 litters from 21 of 48 pairs (44%) after sh ipping. Pairing-to-first-litter intervals were approximately two oestr ous cycles shorter in control animals (39 vs 53 days). Averaged over a ll litters, litter size was higher in control pairs (4.4 vs 4.0). With respect to genotype, control agouti deer mice were less productive th an nonagouti animals, but they reproduced better than nonagoutis after shipping. In control animals, colourmorphs did not differ with respec t to litter production or timing, but agouti pairs had smaller litters (first litter: A: 3.1, a: 4.2) and this difference increased at succe ssive litters (third litter A: 3.9, a: 6.0). After shipping, agouti an imals produced more litters (A: 22, a: 15), and did so earlier (pairin g to birth: A: 47 days, a: 60 days), as well as more frequently (inter litter interval: A: 32 days, a: 51 days). Litter size was also more si milar between genotypes after shipping (A: 4.0, a: 4.1). Overall, cont rol agouti animals produced 37% fewer offspring than nonagouti pairs ( A: 116 neonates, a: 185 neonates), but after shipping agouti deer mice produced 43% more offspring than nanagouti animals (A: 87 neonates, a : 61 neonates). In sum, transport stress suppressed reproduction for s everal weeks after shipping and this suppression was exacerbated in no nagouti deer mice.