Sarcophilus vs Gulo part 5

maternal behaviour of Sarcophilus.
 
Kangaroos have a pattern of ‘maternal jettisoning’ in which a mother, stressed by pursuit by a predator, will jettison her pouch-young. This in itself may be understandable even to a species with a placental mindset, such as the human species. But what is incomprehensible to most persons who know about this tactic is that, when reunited with her pouch-young once the danger has passed, the mother often rejects it, thus condemning it to death. As you know, wildlife carers are universally familiar with this problem in kangaroos and their relatives.
 
Similar, albeit less easily described, maternal ‘lapses’ are known in bandicoots, and I suspect that this is a general pattern among marsupials. From the placental point of view it seems to show a weak maternal instinct, but on reflection it makes sense where the offspring are so small that there is a premium on preservation of the life of the mother, if necessary at the expense of ‘cheap’ offspring in which a limited amount has been invested, and in the context of a continent with limited pressure from predators. Indeed, at an even broader perspective, it makes sense that mammals that ‘gestate’ their offspring in a pouch rather than in a womb should retain the option to sacrifice their offspring; and because marsupials are generally less brainy than placentals it makes sense that mothers should tend to lack the cognitive versatility to ‘realise’ that there is sometimes an unnecessary loss when their hard-wiring causes them to ‘fail’ as mothers once reunited with jettisoned, but fortuitously surviving, offspring.
 
Now, I don’t know much about such behaviour in dasyurids, but I did indeed read, in a newspaper article published on 28 Aug. 200 about the breeding program for Sarcophilus in Monarto Zoo, that “Veterinarian Ian Smith said the joeys were given their first health checks only yesterday because adult females often turned on or deserted their young if they were separated. ‘During the breeding season, we try to maintain a hands-off approach. We’re more concerned that they might leave them and less so that they might eat them,’ Dr Smith said.”
 
Do you see the implication here, i.e. that Sarcophilus is similar to ‘roos and bandicoots in a tendency to lapse in the maternal instinct after temporary separation from pouch-young associated with stress imposed by a potentially predatory species (in this case human)?
 
I have not read anything specific about maternal behaviour in Gulo, and perhaps there are few observations of this anywhere in the world. However, it seems fair to assume that the maternal bond is stronger in this eutherian than in some marsupials, not so? I.e. I suspect that, if suckling, denned offspring were to be lost to a mother and then fortuitously reunited with her unharmed, she would accept them instantly.
 
So my question to you is this: do you think that this is indeed a true difference, i.e. a kind of evolutionary non-convergence or divergence, between Sarcophilus and Gulo? Or on the other hand do you think that Sarcophilus differs in this respect from ‘roos and bandicoots, and that its maternal behaviour is more similar to the eutherian behaviour than is true in some other marsupials? A corollary question is: have you ever heard of any evidence that a mother Sarcophilus carrying relatively large pouch-young, when chased and stressed by a potential predator such as the domestic dog, actually jettisons her pouch-young?

Posted by milewski milewski, June 07, 2022 19:51

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