Behavioural differences between weaner pigs with intact and docked tails: An interview with Dr Rick D’Eath (SRUC)

Rick D’Eath, hello and congratulations to your paper on tail biting in pigs, recently published in Animal Welfare. In this paper, you report a study of how the behaviour of pigs differed between groups where the pigs had been tail docked and groups of pigs with intact tails.

Before we discuss the study itself, can you please tell us a bit more about the problem behind the study?

Tail biting is a behavioural problem affecting growing pigs housed indoors worldwide. Although there are lots of known risk factors, the most important of these seem to be limited access to resources such as feeder space, but also particularly limited access to some material for the pigs to chew, root and manipulate. Tail biting occurs in sporadic ‘outbreaks’ which are difficult to predict or to control. Cutting the pigs’ tails short when piglets are a few days old (Tail docking) is known to reduce the risk of tail biting later in life, but is painful, and is seen by many as being unethical, and that we ought to improve the environment instead of relying on a mutilation as the ‘solution’. It would be great if we could move towards a reduction in tail docking while providing for pigs’ behavioural needs to root and chew. However, there is a lot we still don’t understand about tail biting.

So, behaviour obviously plays an important role in tail biting. You had some very specific hypotheses for this study – please tell us which they were and what they were based on?

Tail docking is known to reduce the risk of tail biting (although not completely), but the reason why tail docking is effective is not clear- one hypothesis is that docked tails are more sensitive, meaning that pigs are more likely to withdraw from the attentions of a potential biter. Another hypothesis is that short tails appear less attractive to biters. Tail investigation and tail-in-mouth behaviours are thought to be pre-cursors to actual damaging tail biting, so how often they occur is likely to affect the risk of a damaging tail biting outbreak. In our study, we observed pigs which were docked or undocked on the same farm, but which were not yet involved in tail biting. We compared their behaviour side by side to investigate whether docked tails were more sensitive or less attractiveness than undocked tails.

I should add that this project was a collaboration between myself and Helle Lahrmann and Torben Jensen- researchers at the Danish Pig Research Centre (SEGES), and the work was carried out at a Danish commercial farm by Mallary Paoli for her dissertation project for the MSc in Applied Animal Behaviour and Animal Welfare (University of Edinburgh).

And what did you find?

Neither of the hypotheses were supported. Docked pigs were not more likely than undocked pigs to withdraw when their tail was nosed by, or taken into the mouth of, another pig, suggesting their tails are not more sensitive. Also, tail-directed behaviours were not more common in the undocked pigs than in the docked pigs, and there was also no evidence that docked pigs held their tails differently or changed their overall level of activity which might have affected the attractiveness or availability of tails to other pigs. So no support for the ‘reduced tail attractiveness’ idea either.

Instead, Mallary argued for another explanation- when tails are longer, pigs are able to hold them across the mouth and bite them more powerfully using the check teeth. Docked tails are too short for this, and biters use only the incisors, resulting in less damage. This idea warrants further investigation.

Unexpectedly, we also found that intact-tailed pigs used enrichment devices in the pen more (ropes, pieces of wood, chains) more than docked pigs, and we have no explanation for this. We also found that larger pigs spent more time in investigatory behaviour, and in tail-directed behaviours, as did females compared to castrated males.

Finally, in one of our undocked groups, there was a tail biting outbreak right near the end of the study. Mallary plotted the behaviour in this pen compared to the others, and found that in the days before the outbreak, activity in this group was comparable to other non-outbreak groups, but tail-directed behaviours were higher, and pigs were more likely to hold their tails down against the body (which is probably a protective behaviour and a sign of pain). Although our data is from a single pen, these sorts of pre-outbreak behavioural changes have been reported by a few other studies using more groups and have the potential to be used by farmers as ‘early warning signs’ to intervene and reduce or prevent damaging tail biting.


Mallary Docked weaner pigs


Journal Article:


For more information about Dr D'Eath's work, please visit his website:


Interview script provided by Dr Anna Olsson