[Show abstract][Hide abstract] ABSTRACT: This chapter provides an overview of the current behavioral and cognitive aspects of emotions in animals and explore the impacts of emotional experiences on the animal's adaptation to its current challenging circumstances. There is evidence that animal welfare results from the animal's perception of its environment and its background. The chapter is structured in four complementary sections. The first one addresses the nature of emotions that the animals can feel which is validated from commonalties in physiological and behavioral responses to dangers across and within species. The second section presents advanced features of the relationships between cognition and emotions originally studied in humans, which are now developed in animals to better access their affective states. The third section is devoted to the relevance of the personality concept, as resulting from both genetics and developmental experience, for assessing animal individuality in emotional behaviors and stress. The last section explores some approaches that can alleviate fear and induce positive affective states, with the potential to mitigate detrimental stress-induced effects on the welfare and health status by eliciting positive emotions in animals.
Genetics and the Behavior of Domestic Animals, 01/2014: pages 81-113; , ISBN: 9780123945860
[Show abstract][Hide abstract] ABSTRACT: The current study presents a novel objective measure for characterizing sexually active groups (SAG 3-5) and relates this measure to other behaviors of lactating Holstein-Friesian cows. Cows in SAG 3-5 were required to participate in a minimum of 1 estrus behavior per 5 min while staying within 3 m (2 cow lengths) of its partner(s) for a minimum of 5 min. Twenty Holstein-Friesian cows were video-monitored continuously through 1 complete estrous cycle (22 d). Standing behavior, SAG 3-5, secondary estrus signs (SEC), and other social and agonistic behaviors were recorded continuously. The period of mounting estrus (MTE) was divided into the 3 parts: prestand, standing estrus (STE), and poststand. The mean durations of MTE, prestand, STE, and poststand period were 12.9 ± 1.84, 4.0 ± 1.93, 7.1 ± 1.44, and 1.8 ± 0.57 h (n = 13). The fractions of time spent in SAG 3-5 during MTE, prestand, STE, and poststand period were 13, 8, 19, and 1% (n = 11). During MTE, cows participated, on average, in 5.8 ± 1.24 SAG 3-5 and initiated 9.5 ± 2.99 mounts, with mean durations of 0.25 ± 0.03 h and 4.00 ± 0.36 s, respectively. The novel measure SAG 3-5 was a sign of long duration not confined only to groups of STE cows. On one day when no cows were in estrus and during the periods 4 to 24 h before and after MTE, no SAG 3-5 behaviors were observed. Luteal-phase cows participated in SAG 3-5 only when the partner was a single cow in estrus. The time spent in SAG 3-5 increased between 1 and 3 h before MTE and the prestand period (3 vs. 8%) and reached a peak level during STE. From STE to poststand, time spent in SAG 3-5 decreased considerably (19 vs. 1%). The observed decrease in nonmutual agonistic behaviors 4 to 24 h before MTE is suggested as an early sign of pre-estrus. Changes in SAG 3-5, agonistic behaviors, and SEC are suggested as indicators of the specific stages of MTE. Increased SEC initiated and SAG 3-5 were indicators of late pre-estrus and early estrus (prestand). Peak levels of SAG 3-5, SEC, and social agonistic behaviors were indicators of STE. A sudden decrease in behaviors, preceded by frequent interactions, was indicative of late estrus (poststand). On the basis of the findings reported here, we propose that SAG 3-5, as well as proceptive and receptive patterns of SEC and agonistic behaviors, be included in estrus detection protocols. Updated knowledge of these behavioral interactions may assist when determining the stage of estrus and the optimal time to breed dairy cows.
[Show abstract][Hide abstract] ABSTRACT: This study reports the effects of peripubertal GnRH receptor inactivation on development of psychophysiological motoric reactivity (PMR; sometimes also called emotional reactivity), plasma cortisol concentrations and the relationship between plasma cortisol and PMR in male and female sheep. The study formed part of a larger trial and utilised 46 same sex twins. One twin remained untreated (control) while the other received a subcutaneous GnRH agonist (GnRHa Goserelin-Acetate) implant every 4th week, beginning at 8 and 28 weeks of age, in males and females, respectively (different, due to sex specific age of puberty). PMR, a measure of an animals' response to social isolation, was measured over a two minute period at 8, 28 and 48 weeks of age, using a three axis accelerometer. During the test period vocalisation rate was recorded. Cortisol was assayed in blood samples collected on a single day when animals were 40 weeks of age. PMR and vocalisation rate were significantly higher in females than males at all ages tested. At 28 weeks of age (20 weeks treatment) PMR was increased in treated males to the level seen in control females, by 48 weeks of age treated males' PMR was significantly less than controls. In females, 20 weeks of GnRHa treatment (28-48 weeks of age) was not associated with differences in PMR. Cortisol concentrations were significantly higher in females than males but were not affected by treatment. Plasma cortisol concentrations were positively correlated with PMR; this relationship being driven by the treated animals in both sexes. The results demonstrate that PMR is sexually dimorphic and cortisol dependent in sheep from at least 8 weeks of age. Importantly, they also demonstrate that long-term treatment of males with a GnRH agonist results in changes in age-dependent development of PMR.
[Show abstract][Hide abstract] ABSTRACT: The objectives of the present study were to describe, in detail, behavior associated with standing estrus (STE) in lactating dairy cows and behavioral changes during complete estrous cycles. Estrus signs were monitored by continuous video recording of 20 Holstein-Friesian (HF) cows housed on an outdoor wood-chip pad during 1 estrous cycle (22 d). Other social behavior was recorded during STE and, for comparison, during 1 selected day when none of the cows were in estrus. Standing stationary when mounted was defined as the primary estrus sign. Anogenital sniff, chin rest, attempt to mount, and mount were defined as secondary estrus signs. Ovarian cyclicity was confirmed by progesterone measurements. This study reports short mean duration of STE (7.1±1.44h) and estrus (mount period; 12.9±1.84h) of the 13 cows expressing these signs. All mounting activities involved at least one cow in, or within 4h of, STE. The most frequent sign during STE was anogenital sniff initiated, followed by chin rest received, chin rest initiated, chase up initiated, anogenital sniff received, mount initiated, head butt, mount received, attempt to mount initiated, push away received, play rub, attempt to mount received, follow initiated, threat received, flehmen, avoid, bellow, and social lick received. Standing and mounting activity in HF cows was inconsistent during estrus, indicating that other signs could be of greater use. The frequency of secondary estrus signs initiated and received increased gradually during the last 12h before STE, revealing significant differences between periods from 4 to 6 and 1 to 3h before STE. A considerable increase in receptive behavior (secondary estrus signs received) was identified between 1 to 3h prior to STE and STE. Both frequent initiated and received behaviors were associated with STE. A significant decrease in the frequency of secondary estrus signs initiated and received occurred 3h after STE. Cows in STE simultaneously predominantly chose the other standing cow as mate and expressed secondary estrus signs more frequently. Based on the results of this study, we suggest that chase up could be regarded as a reliable indicator of estrus and that the changes in proceptive (initiated) and receptive (received) behavior could be used as predictors of different stages in estrus. Knowledge of these behavioral signs may improve heat detection rates and the ability to predict the optimum breeding time for dairy cows.
[Show abstract][Hide abstract] ABSTRACT: Humans and animals are exposed to PCBs and influences on developmental and endocrine processes are among the most pronounced effects. In the present study it was hypothesised that exposure to PCBs may interfere with sexually dimorphic behaviour. To test this hypothesis, behavioural studies in developmentally exposed sheep were conducted. Ewes were orally administered PCB 153 (98 μg/kg bw day), PCB 118 (49 μg/kg bw day) or corn oil from conception until delivery. However, because of accidental cross-contamination occurring twice causing a mixed exposure scenario in all three groups, the focus of this paper is to compare three distinct groups of lambs with different PCB levels (PCB 153 high-PCB 153 h, PCB 118 high-PCB 118 h, and low combined group-LC) rather than comparing animals exposed to single PCB congeners to those of a control group. Lambs were tested between 2 and 6 weeks of age. When LC males started the light/dark choice test in a dark box, they spent significantly more time in the dark part of the pen than LC females. This gender-related difference was not found in groups exposed to PCBs. A significant inhibitory effect on the activity level of males exposed to stress of confinement was found in the PCB 118 h group. In a high stress situation females from PCB 118 h and males from PCB 153 h were less active than their gender counterparts. The results support the hypothesis that intrauterine exposure to PCBs can alter sexually dimorphic behaviour of offspring.
[Show abstract][Hide abstract] ABSTRACT: Wild pigs (Sus scrofa) are only territorial during the peri-parturient period and when young compete for access to teats. In other species, territorial defence is affected by contextual factors including resource quality. Territoriality could be stimulated in species such as pigs by artificial mixing and intensive housing. Test pigs were introduced to a novel opponent for 5min on consecutive days (days 1 and 2) in two locations (home pen of the test pig (P) or a neutral arena (A)) in a randomised block design. On day 1, animals tested in their home pen were more likely to initiate an escalated attack (proportion of pigs 0.43 vs 0.19 in the pen and neutral arena, P
[Show abstract][Hide abstract] ABSTRACT: In mammals, sex specialization is reflected by differences in brain anatomy and function. Measurable differences are documented in reproductive behavior, cognition, and emotion. We hypothesized that gonadotropin-releasing hormone (GnRH) plays a crucial role in controlling the extent of the brain's sex specificity and that changes in GnRH action during critical periods of brain development, such as puberty, will result in altered sex-specific behavioral and physiological patterns. We blocked puberty in half of the 48 same-sex Scottish mule Texel cross sheep twins with GnRH analog (GnRHa) goserelin acetate every 3 weeks, beginning just before puberty. To determine the effects of GnRHa treatment on sex-specific behavior and emotion regulation in different social contexts, we employed the food acquisition task (FAT) and measurement of heart rate variability (HRV). ANOVA revealed significant sex and sex×treatment interaction effects, suggesting that treated males were more likely to leave their companions to acquire food than untreated, while the opposite effect was observed in females. Concordant results were seen in HRV; treated males displayed higher HRV than untreated, while the reverse pattern was found in females, as shown by significant sex and sex×treatment interaction effects. We conclude that long-term prepubertal GnRHa treatment significantly affected sex-specific brain development, which impacted emotion and behavior regulation in sheep. These results suggest that GnRH is a modulator of cognitive function in the developing brain and that the sexes are differentially affected by GnRH modulation.
Hormones and Behavior 10/2010; 59(1):22-7. DOI:10.1016/j.yhbeh.2010.09.010 · 4.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Impacts of individual personality on group distribution were investigated using sheep (Ovis aries) as a model. In an indoor exploration test, individuals who visited <4 (out of 6) objects in a novel environment were classified as 'shy' (n=10), and those who visited 5 or 6 objects were classified as 'bold' (n=10). Nine weeks later, using a series of groups (n=40) of either 5 shy or 5 bold sheep, we measured distribution at pasture and responses to disturbance and the approach of a human handler. When grazing undisturbed, the mean nearest neighbour distance and spread (minimum convex hull area) of shy groups were less than those of bold groups, with shy individuals moving towards one another more often. Shy groups explored a smaller area than bold groups. When disturbed, shy sheep were more likely to stop grazing and move closer together. Shy sheep kept further away from the handler and moved faster when driven. The results demonstrate a link between personality and group distribution, suggesting that our 'shy' and 'bold' individuals may occupy different positions on the shy-bold continuum documented for other species. We discuss implications for diet composition and impacts on vegetation grazed by animals with different personalities.
[Show abstract][Hide abstract] ABSTRACT: Group cohesion in social animals foraging in patchy environments depends on 2 opposite forces, intraspecific competition, and attraction. The decision to leave or stay in a group may vary according to the individual personality. We investigated the role of personality when feeding competition increases as a result of increasing group size. Individuals referred as "bold" and "shy" were identified from an indoor exploration test according to their propensity to leave the group to explore a novel environment, using 12 novel objects placed at increasing distances from the group. Groups of 2, 4, 6, or 8 shy or bold sheep were tested in 45 × 5--m grass arenas, with one 5 × 5--m patch of preferred vegetation at each end. Sheep grazed on or close to these patches, but the number grazing the patches seldom reached more than 4--5 individuals, suggesting that crowding might affect foraging at the highest densities. The smallest groups grazed together on the same patch, but there was an increasing likelihood of splitting into subgroups as group size increased, with equal-sized subgroups most commonly grazing the 2 patches simultaneously. This effect was greatest in bold sheep, which tended to split into subgroups at smaller group sizes than shy sheep. This study provides new insight into the mechanisms by which group-living herbivores distribute themselves across patchy resources in a way that minimizes interference competition and demonstrates the importance of individual variability for spatial organization at the level of the group. Copyright 2009, Oxford University Press.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to test the existence of a “fearfulness” trait in horses, by testing the stability across situations and over time of the responses to different fear-eliciting situations. It was also to identify which behavioural parameters are the best indicators of this trait. Sixty-six Welsh ponies and 44 Anglo-Arab horses were successively tested at 8 months and 1.5 years of age. Of these, 33 Welsh ponies and 21 Anglo-Arabs were also tested at 2.5 years of age. At each age, they were subjected to four test situations. The first test involved the introduction of a novel object in the test pen (novel object test). In the second test, a novel area was placed in the pen between the horse and a bucket of food, to determine the time the horse took to cross the area (novel area test). Finally, the third test consisted in suddenly opening an umbrella in front of the horse while it was eating (surprise test). During these tests, many behavioural parameters were recorded. A fourth test consisted of a surprise test during which the horse was held by a handler while its heart rate was measured. Spearman correlations were used to identify links between behavioural parameters measured during different tests and between different ages.Reactions to the first three tests showed consistency between them and over time. Among all the behavioural parameters measured during these tests, some presented high stability over time and were well correlated with behaviours expressed during other tests, indicating they are the best indicators of a fearfulness trait: the frequency of licking/nibbling the novel object, the time to put one foot on the novel area and to eat from a bucket placed just behind it, and the flight distance and the time to eat under the opened umbrella. The stability across responses expressed in various fear-eliciting events and over time from 8 months to 2.5 years of age suggests the existence of a ‘fearfulness’ trait in horses.The different indexes of heart rate measured or calculated during the surprise effect present limited stability over time and almost no correlation with the behavioural parameters measured during the other three tests. We conclude that, in contrast to the previously mentioned behaviours, these are not reliable measures of a temperament trait.From a practical point of view, this study shows that it is possible to identify a horse's level of fearfulness as early as 8 months of age using the first three tests.
[Show abstract][Hide abstract] ABSTRACT: A clutch of young chicks housed with a mother hen exhibit ultradian (within day) rhythms of activity corresponding to the brooding cycle of the hen. In the present study clear evidence was found of ultradian activity rhythms in newly hatched domestic chicks housed in groups larger than natural clutch size without a mother hen or any other obvious external time-keeper. No consistent synchrony was found between groups housed in different pens within the same room. The ultradian rhythms disappeared with time and little evidence of group rhythmicity remained by the third night. This disappearance over time suggests that the presence of a mother hen may be pivotal for the long-term maintenance of these rhythms. The ultradian rhythm of the chicks may also play an important role in the initiation of brooding cycles during the behavioural transition of the mother hen from incubation to brooding. Computer simulations of individual activity rhythms were found to reproduce the observations made on a group basis. This was achievable even when individual chick rhythms were modelled as independent of each other, thus no assumptions of social facilitation are necessary to obtain ultradian activity rhythms on a group level.
[Show abstract][Hide abstract] ABSTRACT: A temperament trait is generally defined as individual differences in behaviour that are present early in life and relatively stable across situations and over time. The aim of this study was to test the existence of a trait «gregariousness» in horses, by testing the stability across situations and over time of the responses to different social events. Sixty-six Welsh ponies and 44 Anglo-Arab horses were successively tested at 8 months and 1.5 years of age. Among them, 33 ponies and 21 horses were also tested at 2.5 years of age. They were submitted to four test situations: isolation and separation from, attraction towards and passing conspecifics. We carried out the analysis using each of four test groups as a unit (e.g. 33 Welsh ponies born in 2001, tested in isolation).Isolation and separation stood out as tests that showed a high consistency within test, across tests and across time. The most interesting behavioural parameter was the frequency of neighing, which was well correlated with other parameters measured in the same tests, such as defecation, locomotion and vigilance, as well as across the 3 years (e.g. for separation test: 0.41
[Show abstract][Hide abstract] ABSTRACT: During a behavioural test, the test animal's perception of the test situation may change, e.g. as a result of habituation. This change can occur within a test or between repetitions of a test. It is particularly important in the arena test because in an approach–avoidance situation, the negative stimulus may not be followed by the negative consequences it is initially associated with (tested ‘in extinction’).In this experiment, we tested single sheep for 10min in a situation of conflict between either being too close to a negative stimulus (human being) or too far away from a positive stimulus (conspecifics). The test was carried out over four consecutive days, each sheep being tested once a day. We recorded the distance between the test sheep and the conflicting stimuli, the occurrence of urination and rumination and the duration of sniffing during the test. Principal components analysis (PCA) revealed three main components of distance; the average (76%), a linear (11%) and a quadratic change across time (6%). Distances decreased within and across tests and the occurrence of urination decreased, while rumination and sniffing increased across tests. These changes of behaviour across time suggest that extinction of the conditioned response occurred within as well as across tests. These results highlight the importance of choosing the appropriate duration for a test, particularly when the test is carried out in extinction.
[Show abstract][Hide abstract] ABSTRACT: This paper describes a test for gregarious grazing animals, which measures trade-offs between feeding and social companionship. Four groups of 10 female Scottish Blackface sheep were used for the study and bowls containing food pellets were used to draw individuals away from the group. The sheep were individually observed four times (once every 2 weeks) for 30min each in a 65m×33m grass arena, while the rest of the group were confined at one end. The first time was a control test (C) with no food bowls. Other three times were pellet tests (P1–P3), with 12 bowls placed at 5-m intervals along the length of the arena and 25g food pellets in each bowl. In addition, within-group sociability indices (SIs) were measured while the sheep grazed together during the weeks without tests.Both the maximum and average distance from the group were higher in P1–P3 than in C. The maximum distance increased between P1 and P3, with only three animals failing to reach the furthest bowl in P3, although average distance from the group did not change between runs. The time taken to visit all the bowls for the first time decreased between P1 and P3, although the total number of bowl visits increased. There were positive correlations between runs in average distance from the group and the total number of bowl visits. In each group, the five sheep with the highest SI values had lower maximum and average distances, tended to take longer to visit the bowls for the first time in P1 and were more vigilant than the rest of the group. It is concluded that the test can detect differences in the willingness of individuals to move away from a social group and could be used to compare different species or breeds of animal, as well as individuals within species, or to compare the attractiveness of different social companions.
[Show abstract][Hide abstract] ABSTRACT: The term ‘leadership’ has been used in several different senses, resulting in very different ways of identifying leaders and apparently inconsistent conclusions on how leadership is determined in herbivores. We therefore propose the following definitions: (i) a leader is the individual that is consistently the one who initiates long-distance, spontaneous group movements toward a new feeding site and (ii) long-distance spontaneous group movements are movements which happen when an animal changes activity and location and is immediately followed by a similar change in activity and location by other members of the group. Using these definitions, we tested for consistency of movement order across time and situation within a group of fifteen 2-year-old heifers. We found that the same individual was recorded as the very first animal in 48% of movements toward a new feeding site and could therefore be identified as the ‘leader’. We also showed that movement order when the animals entered an experimental plot, or progressed slowly through the field during a grazing bout, did not produce the same result. This method, which enables us to identify leaders in groups of animals at pasture, should improve our knowledge of how leadership is determined in grazing herbivores.
[Show abstract][Hide abstract] ABSTRACT: We describe a method for quantifying relative sociability within a group of animals, which is defined as the tendency to be close to others within the group and based on the identification of nearest neighbours. The method is suitable for groups of animals in which all individuals are visible and identifiable and has application as a tool in other areas of behavioural research. A sociability index (SI) is calculated, which is equivalent to the relative proportion of time that an individual spends as the nearest neighbour of other animals in the group and is scaled to have an expectation of 1.0 under the null hypothesis of random mixing. Associated pairs, which are animals seen as nearest neighbours more often than would be expected by chance, are also identified. The method tests for consistency across a number of independent observation periods, by comparison with values obtained from simulations in which animal identities are randomised between observation periods. An experiment is described in which 8 groups of 7 grazing sheep were each observed for a total of 10, one-hour periods and the identities and distances away of the 3 nearest neighbours of each focal animal recorded at 5-min intervals. Significant within-group differences in SIs were found in four of the groups (P
[Show abstract][Hide abstract] ABSTRACT: In order to find out whether exposure to environmental pollutants (EP) present in sewage sludge can change the behaviour of sheep, we compared the behaviour of two groups of 5-month old lambs (Ovis aries) with respect to their emotional reactivity and exploratory behaviour. One group (treated, T) comprised the offspring of ewes who had been kept throughout their lives on pastures with slightly elevated, environmental levels of pollutants, as a result of the application of sewage sludge at rates used in normal practice. The other group (control, C) were the offspring of ewes whose pastures had been treated with inorganic fertiliser. During a 1-min period in the weigh crate, T lambs were less reactive than C lambs, but vocalised more. Exploratory behaviour showed a clear sex difference, with female C lambs exploring more than male C lambs. However, this difference was not found in the T lambs, where both males and females showed high levels of exploration. This points to a demasculinising effect of exposure to higher pollutant concentrations with respect to exploratory behaviour. These observations demonstrate the need to take account of the effects of combinations of pollutants, even at very low, environmental concentrations, and further highlight the usefulness of ethotoxicology for the study of biological effects of environmental pollutants.
Science of The Total Environment 11/2004; 332(1-3):101-8. DOI:10.1016/j.scitotenv.2004.04.012 · 4.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The experiment reported was designed to test two hypotheses: that prenatal undernutrition (a) increases emotional reactivity and (b) impairs cognitive flexibility in sheep. The mothers of one group were fed live weight maintenance requirements throughout pregnancy (control, C) while those of another group were fed 50% of that amount from days 1 to 95 of pregnancy and 100% from then onwards (prenatal undernutrition, PU). At 18 months of age, PU sheep were more active during restraint (P < 0.05) and approached a novel stimulus more slowly (P = 0.02). In response to a sudden stimulus, PU males and C females showed a higher initial level of locomotion compared to C males, which only gradually declined, while PU females started at a high initial rate, changing rapidly to immobility. In a T-maze, PU resulted in a shift of side preferences (laterality) from a general right-bias to neutrality in males and to a left-bias in females (P < 0.05). In the two reversal tasks, C males and PU females had a preference for one side over the other, while PU males showed no preference. In contrast to C males, PU males failed to improve their learning speed from the first to the second reversal (P < 0.05). It is concluded that PU can lead to increased emotional reactivity and changes in side preference in both sexes and impaired cognitive flexibility in males. Undernutrition during pregnancy, therefore, not only affects the welfare of the dam, but also the personality of her offspring.
Behavioural Brain Research 05/2004; 151(1-2):25-35. DOI:10.1016/j.bbr.2003.08.003 · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The dominance structure in an established group of sheep is often difficult to determine in the field, because of the low frequency of agonistic interactions, often resulting in some pairs of animals not interacting at all in the observation period. A solution to this problem is to test each pair separately in a competitive situation. The most frequently used test involves competition for food after a specific period of food deprivation, but to date, there is no agreement as to the optimum length of time the animals should go without food. In this experiment, we compared competitive behaviour at different lengths of time after a meal.The experimental animals were a group a of 10 1-year-old, female Scottish Blackface sheep (45 dyads), who had access to dry grass pellets twice daily, from 07:00 to 08:00h and from 19:00 to 20:00h. They were tested in pairs for 5min immediately after and 2, 4, 6 and 8h after the end of the morning meal. In the test arena (4.5m×4.5m) a feed hopper provided access to feed to only one sheep at a time. We recorded aggressive interactions, such as blocking, threats and butts, as well as non-aggressive interactions (nudges), the time spent at the feeder, and the number and type of displacements (aggressive or non-aggressive). The number of displacements was also recorded in the home pens during ten 45-min periods of group feeding.Blocking behaviour showed the clearest difference between the two sheep in a pair and was, therefore, used as the main indicator of dominance. Its occurrence increased as the time since the morning meal was increased and decreased in the course of the 5min tests. Consistency between pair-tests and group observations was greatest in the test 8h after the previous meal, but the difference in consistency between the 2 and 8h tests was small. Recording the behaviour for more than 2min of the 5-min test did not increase the consistency of the data.We suggest that a period of at least 2h of food withdrawal is necessary to generate sufficient motivation for a competition test and to mask differences in feeding motivation between individuals. While the performance of dominance-relevant behaviour increased with time since the last meal, a period of 4h may be sufficient to provide high-quality data. We also suggest that the test duration can be reduced to 2min.