The duration of lactation in feral coypus (Myocastor coypus)

The frequency of consecutive reproductive stages in a post mortem sample of 423 lactating coypus was used to estimate the mean post partum interval (D pp ) and the mean duration of lactation ( D 1 ). The estimates required a number of assumptions but the most important involved the validity of making time specific inferences from an “age” series. Variation statistics could not be calculated using conventional techniques and the jacknife method of estimation was used to obtain variances of the means and 95 % confidence intervals. D pp was estimated as 21 ± 0–8 weeks. Some observations of retrapped wild animals showed that some animals conceived at an oestrus which occurred within a day or two of parturition. D l was estimated in four different ways, three of which were quite closely related: these averaged 8–4 ± 10 weeks. But the fourth estimate, which is equally valid, was 70 weeks. A weighted average of the four estimates was 7–7 weeks with 95 % confidence limits of c . ± 10. The average suckling period of five captive females was 10–9 weeks. The most likely interpretation of the 42 % difference between this value and the estimate for wild females is attenuation as a result of a reduced nutrient intake in the feral population. D L is substantially longer than predicted from an expression relating maternal weight to D L in other mammals. This may be part of a maternal care strategy that centres on protection of space, and possibly of a food supply for milk production, rather than on defence of the young.