Kune Kune Research

 

The main goal of our research with pigs is to test the hypothesis – implicit in most theories of the evolution of advanced cognition – that socio-cognitive abilities become apparent in groups of social animals if they a) are kept in conditions similar to the natural environment and b) if they are forced to use those abilities in appropriate, challenging circumstances.

To test this hypothesis, we have been conducting a series of experiments that have been used in the literature to examine the socio-cognitive abilities of non-human animals.

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Pigs show a number of features indicative of social complexity but as omnivors only modest technical skills.

Importantly, to bring their true potential in the social domain to the front, the research is done with free-ranging pigs (kept in semi-natural environments), where they (slowly) grow up, forage naturally, develop a natural group structure (sounder) and live for years (from birth to their natural end).

Scientists from the Unit of Comparative Cognition 2 observe the behavior of the pigs (with the aid of video cameras) and conduct controlled experiments (with the aid of technical equipment) on their socio-cognitive abilities.

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As social cognition may be used as a behavioral strategy to keep the social system in balance and stress level low, we collect saliva samples (with cotton swabs) of the well-trained pigs. Proper immune function is crucial to animal and human health, and stress is one major factor modulating different aspects of immunity. Colleagues form the Comparative Medicine 4 unit of the institute are involved here.

The results of these investigations are reflected upon ethically. That is to say that they are viewed in a context of elevated importance, in particular in relation to their relevance for the human-animal-relationship and animal ethics. Colleagues form the Ethics unit 5 of the institute are involved here.

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Discrimination and categorization

Scientists as well as farmers are increasingly interested in the mental capacities of pigs. Still, our knowledge about perceptuo-cognitive abilities, especially in the visual domain, is lagging behind.

In the few studies conducted so far pigs have failed to discriminate pictures of conspecifics, which contrasts with findings in other farm animals. From the perspective of human-animal relationship it would be especially interesting to know what and how pigs learn about humans, for instance, if they would learn to visually discriminate people.

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All pigs are trained to respond to their individual names when called and follow the experimenter voluntarily to the testing compartment. If one individual is not motivated and refuses to follow, it will not be trained or tested on that day.

We conducted an experiment with 33 of our pigs that lived for almost two years in close relationship to humans. The task afforded to discriminate between two views of the heads (front and back) of 10 women presented on a computer screen (a). The computer-controlled training excluded the influence of human experimenters and any other cues than the visual ones. Altogether 31 subjects reached a high (> 80%) and stable learning criterion.

This discrimination performance, which could not be achieved by using simple features like size, color or brightness, challenges the one of a previous study in which pigs failed to discriminate between only two pictures of conspecifics.

A generalization test, in which the pigs were asked to spontaneously discriminate the two head views from further 16 women (b), corroborated this astonishing achievement. The average score of 84% correct responses suggests that the pigs had not simply stored the training pictures together with the respective contingency in their memory but have learned the task by open-ended categorization.

A final set of tests with inverted and scrambled pictures and ones with missing facial parts aimed at determining which features of the stimuli the pigs used as discriminatory cues (c-g). At least for some pigs these features were face-specific or orientation-dependent, as changes of the facial parts (eyes or mouth) or of the orientation of the face were avoided.

These findings revise some pessimistic conclusions drawn from previous studies and challenge the still dominant view about the poor visuo-cognitive abilities of pigs. The use and training of all senses and the fostering of their cognitive talents is likely a form of cognitive enrichment in conventional housing systems and a way of enhancing their welfare.

Wondrak, M., Conzelmann, E., Veit, A., & Huber, L. (2018). Pigs (Sus scrofa domesticus) categorize pictures of human heads. Applied Animal Behaviour Science, 205, 19–27.

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Social learning

Learning by observing others is especially beneficial for young and naïve individuals. The relationship to the social partner is thus important. While peers are often used as demonstrators to test for social learning abilities in a species, thereby studying horizontal transmission of information, we focused on the vertical transmission of information, i.e. learning across generations.

Half-a-year-old piglets were first exposed to their mother or aunt pushing one of two differently coloured bars to either the left or right side to open a sliding door, and were then tested after 1 min, 1 h and 1-day retention intervals.

The observers recalled the movement of the door, rather than using local or stimulus enhancement. Furthermore, the pigs used the demonstrated opening technique and even remembered it after a delay of 24 h. Nonexposed piglets did not show a side bias during their first encounters with the apparatus; however, habit formation was at play during later test sessions and was possibly the reason for long-term memory of the self-acquired techniques.

Altogether, this study revealed that piglets learned how to solve a manipulative foraging problem from both their mother and their aunt, probably by acquiring some information through observation and then memorizing it for up to a day.

Veit, A., Wondrak, M., & Huber, L. (2017). Object movement re-enactment in free-ranging Kune Kune piglets. Animal Behaviour, 132, 49–59.

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Honest signaling in domestic piglets

A collaborative study with Prof. Tecumseh Fitch and Maxime Garcia (University of Vienna, Dept. Cognitive Biology) investigated the correlation between body size and grunt calls of growing domestic piglets.

The information conveyed in acoustic signals is a central topic in mammal vocal communication research. Body size is one form of information that can be encoded in calls. Acoustic allometry aims to identify the specific acoustic correlates of body size within the vocalizations of a given species, and formants are often a useful acoustic cue in this context.

We conducted a longitudinal investigation of acoustic allometry in our piglets, asking whether formants of grunt vocalizations provide information concerning the caller’s body size over time. On four occasions, we recorded grunts from 20 piglets, measured their vocal tract length by means of radiographs (X-rays) and weighed them. Controlling for effects of age and sex, we found that body weight strongly predicts vocal tract length, which in turn determines formant frequencies.

We concluded that grunt formant frequencies could allow domestic pigs to assess a signaler’s body size as it grows. Further research using playback experiments is needed to determine the perceptual role of formants in domestic pig communication.

Garcia, M., Wondrak, M., Huber, L., & Fitch, W. T. (2016). Honest signaling in domestic piglets (Sus scrofa domesticus): vocal allometry and the information content of grunt calls. Journal of Experimental Biology, 219(12), 1913–1921.

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Social Structure

The social structure of domestic pigs living in a mixed-sex-group in a semi-natural environment has rarely been investigated. The aim of this work package is the identification and description of the social structure of the whole pig herd, including an assessment of the dominance hierarchy, of the network of relationships (social network analysis), and the dynamic changes within.

The social structure is determined by a variety of interactions between individuals and plays a crucial role in group-living species.

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Informed forager

When some members in the group know where food is and others not, the latter may start scrounging from the former. Tactical deception has been suggested as a counter-strategy by informed foragers. In this experiment, adapted after Held et al. (2002, 2010), pairs of pigs are tested in competitive foraging trials.

We trained 10 individuals of middle rank to find food in (always) one of five locations (informed foragers, IF) and 10 higher and 10 lower ranking pigs (non-informed foragers, NI) to find food somewhere in the foraging arena (but never at the same place). The relationships between the individuals and their position in the social group (sounder) has been determined on the basis of a social network analysis, which was done during the half year before the experiment.

On test days, each IF pig has been given access to the arena first alone to find food at the known location and then together with a NI pig (either a higher or a lower ranking individual), thereby starting from two adjacent waiting areas at the same time.

We coded which one of the two pigs gained access to the food first and whether one was displaced by the partner. The work is in progress. We will see if some IF pigs will develop behavioral strategies against exploitation.

Held et al. (2002). Foraging pigs alter their behaviour in response to exploitation. Animal Behaviour, 64, 157-165

Held et al. (2010). Domestic pigs, Sus scrofa, adjust their foraging behaviour to whom they are foraging with. Animal Behaviour, 79(4), 857-862.

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Personality

The reaction of an animal to an unfamiliar stimulus is partly determined by its coping style. Proactive and reactive coping styles help explain differences in behavioral response of animals, which live in similar circumstances, and would therefore be a good indicator for animal welfare.

So far little is known about coping mechanisms in free ranging pigs, that are able to express their natural behavior and are therefore more likely able to use the innate potential to get along with stressful situations.

In several experiments we have been investigating the personality of sows and their piglets and their development over time. By using standard test procedures for pigs (Open Field Test and Novel Object Test), we tested for anxiety, exploration, and the reaction to social isolation.

In general, the results were quite surprising. In contrast to barren-housed pigs, our free-ranging Kune Kune pigs didn’t show great interest in the novel objects introduced. The pigs obviously showed higher interest in fresh grass than in the novel object.

A reason for this may be that our pigs we used live in a highly enriched environment where they are exposed to many novel stimuli every single day.

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Saliva sampling methodology

An essential aim of the pig project is to apply saliva sampling methodology in free-ranging pigs and piglets at the Outdoor Pig Lab (OPL) of the Haidlhof Research Station for routine analyses of salivary stress and immune biomarkers (e.g. cortisol, IgA and novel markers). Our aim is to use non-invasive saliva sampling methodology in free-ranging pigs and piglets, including training procedures, and finally, standardization (identification of suitable devices, sampling duration, validation) for routine sampling at the Haidlhof Pig Lab Research Station.

Saliva samples were collected weekly from each individual at two timepoints (9-10 am; 2-3 pm). To absorb pig saliva, commercial hydrocellulose/cotton swab devices were gently placed into the pig’s mouth for 40-60 seconds. Prior to analysis, samples were stored at -20°C. Salivary cortisol was analyzed with a highly sensitive EIA. Moreover, the piglets’ suckling behavior was monitored daily.

Wondrak, M., Palme, R., Tichy, A. & Glenk, L.-M. (2015). Salivary cortisol secretion of semi-feral pigs under natural weaning conditions. Poster at ISWE (International Society of Wildlife Endocrinology) Conference, Berlin, Germany, 12-14 Oct 2015.

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Transportation stress

Short-term stress responses associated with transportation have been well-described in various livestock including pigs. We aimed to measure stress responses non-invasively by analysis of salivary cortisol in semi-feral pigs. Moreover, salivary NGAL (Neutrophil Gelatinase-Associated Lipocalin) was monitored as an additional marker of stress-related immune reactivity.

Three semi-feral gilts had to be transported for 90 minutes to a novel housing environment. Saliva samples from each individual were collected at resting conditions (baseline), before and after loading on the livestock trailer and after arrival at the destination (recovery). To absorb pig saliva, commercial cotton swab devices were gently placed into the pig’s mouth for 40-60 seconds. Prior to analysis, samples were stored at -20°C. Salivary cortisol was analyzed with a highly sensitive EIA and NGAL was determined with ELISA (Pig NGAL ELISA Kit, BioPorto).

Cortisol levels increased twofold in one individual and sixfold in two individuals from baseline to post-transportation, reflecting the timepoint during road transportation. During the recovery phase, cortisol levels decreased, reaching baseline values. In contrast, NGAL baseline levels were higher compared to post-transport.

Glenk, L.-M., Palme, R. & Wondrak, M. (2015). Non-invasive stress-measurement during road transportation of semi-feral Kune Kune Pigs. A Pilot Study. Poster at ISWE (International Society of Wildlife Endocrinology) Conference, Berlin, Germany, 12-14 Oct 2015.

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Clever Pig Lab