This blog post is provided by Laura L. Griffin and tells the #StoryBehindthePaper for the paper “Artificial selection in human-wildlife feeding interactions“, which was recently published in the Journal of Animal Ecology. In their study, they link human-wildlife feeding interactions with the production of heavier offspring, identifying these interactions as a driver for artificial selection. Here, author Laura L. Griffin tells us more.

Humans are constantly encountering wild animals – whether intentionally or unintentionally, and whether we realise it or not. Typically, these encounters occur through activities such as hunting, fishing, hiking, or tourism, amongst many others, and unravelling how these activities impact the wildlife around us has become one of the most interesting challenges for modern ecologists. We now know that, in general, our activities have a number of previously unrealised effects on wild populations, spurring the need to identify and explore these impacts further.

One human activity that has become increasingly popular in recent times is hand-feeding wild animals. People often say that it allows them to feel a connection with these animals, that they believe that they’re helping them in some way, and that it makes for good content on their social media accounts. In fact, videos and pictures of people feeding wildlife quite often go viral across different social media platforms. Nevertheless, it is of fundamental importance that we pause to explore how these interactions are affecting the wildlife involved – especially as these interactions are typically self-motivated, meaning that the offered foods are usually not part of these animals’ natural diet.

Our study was based in Phoenix Park, Dublin, Ireland; the largest, walled park in any European capital and host to roughly 10 million visitors per year. The resident fallow deer population, present in the Park since the mid-1600s, is now commonly fed by well-meaning visitors, prompting concerns for deer welfare. In particular, there is concern about whether this feeding is occurring randomly, so all deer receive some food, or whether it only involves a few individuals.

We have now revealed that the likelihood for a deer to interact with people for food (a behaviour that we refer to as ‘begging’) falls on a repeatable spectrum, with only about 24% of the population actually consistently begging for food. In fact, we could broadly categorise the entire population into three categories: consistent beggars, occasional beggars, and rare beggars.

As expected, we were able to show that those deer that beg more also receive a larger amount of human foods – including bread, crisps, carrots, apples, and biscuits. This means that the deer at this site have drastically different diets from one another, i.e. those on a more natural diet made up primarily of grass (rare and occasional beggars) and those that are on a human-supplemented diet (consistent beggars). Immediately we began to wonder whether this intake of human foods could be benefiting or negatively affecting these consistent beggars in terms of reproduction. For example, if human food allows them to invest more heavily in in-utero fawn development, similarly to them receiving a high-concentrate feed, then you would anticipate that the offspring of consistent beggars would be considerably heavier than the offspring of other mothers in the Park. Other research at this site has shown that heavier offspring have a distinct survival advantage during early life (Amin et al. 2022) which would mean that, if the ingestion of human food results in heavier offspring, artificial selection of these mothers’ genetics could be at work.

We measured the birthweights of 134 fawns over 3 years, and found that the fawns of mothers that were classified as consistent beggars were significantly heavier than fawns of mothers classified as occasional or rare beggars. Notably, these mothers occurred in the same herds, across the same grazing areas, and all had equal opportunity to interact with people – leaving this difference in begging behaviour as the defining difference that could be causing this disparity in birthweight. It also stands to reason that if this is occurring in this population, then it is very likely also the case across other populations and species as well. This marks these human-wildlife feeding interactions, for the first time, as a driver for artificial selection of this begging behavioural trait, which is likely associated with bolder personality types. Now that this has been identified at our site, we can work to test methods aiming to reduce these impacts through public education, which can also be applied to other sites experiencing similar interactions (Griffin et al. 2022b).

Further reading

GRIFFIN, L. L., HAIGH, A., AMIN, B., FAULL, J., NORMAN, A. & CIUTI, S. 2022a. Artificial selection in human-wildlife feeding interactions. Journal of Animal Ecology.
GRIFFIN, L.L., HAIGH, A., CONTEDDU, K., ANDALOC, M., MCDONNELL, P. and CIUTI, S., 2022b. Reducing risky interactions: Identifying barriers to the successful management of human–wildlife conflict in an urban parkland. People and Nature.
AMIN, B., VERBEEK, L., HAIGH, A., GRIFFIN, L.L. and CIUTI, S., 2022. Risk-taking neonates do not pay a survival cost in a free-ranging large mammal 2.