It is important for rehab facilities to recognise that wild seal pups never normally eat prey that they have not caught and killed themselves. they do not go through a weaning stage (like wild cats and dogs) of eating dead prey brought to them by their mother. So far as we know, they make a transition directly from nursing from their mother to independent foraging for small, live prey.
Therefore, when caring for a pup of nursing or weaning age in rehab, it should be understood that it is not following a natural pattern to train the pup to eat dead fish. It is a frequent misconception in rehab centres that a nursing pup should be 'weaned on to solids', and that successful training of pups to take dead fish in rehab will somehow help them to adapt to independent life in the wild after their release. It will not - in fact a pup so-trained will have to 'unlearn' the rehab fish-feeding pattern and substitute the totally new pattern of foraging behaviour and catching live prey.
It is for this reason that we feed pups only a milk formula until their release. This mirrors the natural situation of nursing from the mother until weaning and nutritional independence. Our tracking studies have shown that our pups make the transition to normal diving and foraging behaviour immediately after release.
We have used the milk formula successfully in feeding two pups who were from about 6-9 weeks of age in rehab (Cecilia - 1996, and Leo - 2001), and one pup for a few days in November. a four months of age (Olly - 2002). However, for a pup taken into rehab at 3 months of age or older, it may be less detrimental to feed it on dead fish (if that is more convenient for the carer), since the pup will probably alrealy have established natural feeding patterns; however, the period of rehab should be kept as short as possible in order for the natural feeding pattern not to be lost.
This issue is particularly important to the feeding of grey seal pups in rehab. Grey seals seem to be more opportunistic in their feeding patterns than harbour seals, and very easily learn 'aberrant' feeding patterns, such as feeding from fish scraps in harbours, following fishing boats, and raiding fishing nets and fresh-baited creels. A grey seal that has been trained to eat dead fish in rehab may be more likely to adopt this type of feeding strategy after release, which may lead it into conflict with fishermen and possibly an untimely death.