Does cold stress make mothers kill their pups?

This is what a team of researchers claim in a short report published this spring in Journal of Animal Science and Technology. They base this claim on a study in which they housed female periparturient mice in different environmental temperatures (20-23C versus 10-15C) and counted pups.

Based on what I know about on mouse maternal behaviour and pup survival, a topic I have been researching for more than a decade, I don’t believe that cold stress makes females kill their pups. In fact, our research shows that females often eat their already dead pups, but rarely ever do they actively kill pups.

But if presented with convincing data, I would of course change my mind. The important thing about the short report cited in the first paragraph is that it did not present any data on maternal behaviour. The only data presented is about pups – numbers born and numbers surviving.

A few years ago, these reflections would not have left our informal research group discussions, but now there are public fora for this kind of critical discussion. So I just wrote my first PubPeer comment.

Congress blogging Day 1 PM: ISAE, PEI, Canada

The afternoon session the first day started with Temple Grandin’s plenary talk. The title captures what Temple Grandin has really spent her entire career doing: Crossing the divide between academic research and practical application of ethology on farms. As always, her talk was an energizing tour-de-force full of practical advice. She started by underlining that people in The Field don’t know that applied ethology exists, and that to reach them you need to simplify, simplify, simplify (not because they are not intelligent but because there is very little time to convey whatever concept). As an example of how to be clear, simple and specific in formulating guidelines: don’t write “sufficient space”, write “enough for all pigs to lie down at the same time”. Equally worth sharing is her final reflections which paraphrased went something like “I’ve spent my entire life designing slaughter houses, now they’re busy developing artificial meat, in 20 years people may be thinking that my work was unethical”. (I hope many of us are making that kind of reflection at least occasionally, because it is an important one. It is also one I hope to be able to explore in a future, ISAE-related project).

In the afternoon parallel session period, I of course followed the laboratory animal science strand. It started in an unusually coherent way, with two talks reporting work on the same cohort of mice, by Aimée Marie Adcock And Emma Nip. Their work is based on housing female mice in trios in either standard or enriched cages

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As the photos show, this study brings back the environmental enrichment methodology that is hardly seen in laboratory animal welfare studies today, the one where the animals are given a radically richer environment, rather than the minimal-improvement-within-what-is-still-standard. Another interesting approach in this study is that the animals were housed in trios of three different strains (DBA, C57Bl6, Ball/c), which since they are distinctly coloured means that individual animals can be followed on videos without the need for individual marking.

The two subsequent talks reported studies done in collaboration with other animal users. Sophie Brajon reported results from our work on perinatal mortality in laboratory mouse breeding, where we followed mice in two different breeding facilities. Brianna Gaskill’s work took up recommendations made a decade ago by Pascalle van Loo for reducing aggression in mice and applied them on mice in a toxicology study. Once this work which is still under analysis, both studies have potential to influence recommendations for housing and managing mice. This may also be true for the last study reported in this session, by Becca Franks on curiosity in zebrafish, because indeed the way this species is kept has very little to do with their natural behaviour.

Curiosity also drove me to take part in the final event of the day, a workshop on Animal Welfare Assessment Contest. I have seen this activity discussed in ISAE since more than a decade, but in all honesty, I never engaged with  this North American concept of competing in how to evaluate animal welfare. It has always seemed rather alien to me: in Europe sports is the only activity we compete in at universities – outside the ongoing silent competition for the best marks of course. In a well organized session we got the taste of a real competition, got to try our hand at evaluating the welfare of working donkeys in two different contexts and watch the impressive performance of students with actual competition experience (Megan La Follette on the photo below).

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What’s the problem with this photo?

I was asked to comment on what the problem is with the stock photo above. RSPCA did well in pointing out that there is a problem, even though they somehow missed the opportunity to explain what the problem is!

The photo shows a mouse female and her litter. Based on that the pups have some fur but don’t yet have their eyes open, I would guesstimate that they are perhaps a week old. Mice are an altricious species, which means that the young are born in an undeveloped stage and are fully dependent on parental care for basically everything during their first week of life. They do develop very fast, and are ready to leave the nest at about a month of age, and sexually mature just a few weeks later. But at the stage of development in this photo, they aren’t capable of doing very much. The place for such young pups to be is the nest that their mother (or parents, males share the parental care if they can, although under laboratory conditions they may or may not be present) have prepared. That provides them with the thermal microenvironment they need – which needs to be warmer than that of an adult mouse given their poorly developed fur.

Judging from own experience of how long it takes to get a good photo of animals, by the time this photo was taken, the pups were no doubt cold. But that is only part of the problem. Anyone who has seen a professional photo session, or having had their photo taken in a studio, knows that this involves lots of bright light and reflectors. Well, this is precisely the kind of environment neuroscientists use to test anxiety in mice – an open and brightly lit space. Mice are nocturnal animals who spend their lives in tunnels and rarely venture out in the open light, and being forced to be in an environment which in nature would be dangerous is stressful for any mouse. Most likely, it is even more stressful for a female when her rather helpless pups are also exposed in this way.

If you want to learn more about our research in this field. check out the Alive Pup Project. But before you go there, let me just reflect on the different ways of making photos and for which purpose. You will see that in the Alive Pup Project we also show photos of pups taken out of their nest. But these photos were taken when the pups were weighed and inspected as part of a research project aiming to elucidate factors behind pup mortality. This is a big problem in laboratory mouse breeding, and research into the problem requires collecting data. In contrast, it is possible to make nice photos of mice in environments which are less stressful for them the one illustrated above

Still, I need to admit that we have also used stock photos of mice in unnatural environments. We simply did not think. Now we will!