Abstract: Knowledge about social recognition and memory in animals can help us to determine appropriate management and husbandry techniques. In this study, we used a habituation–discrimination procedure to investigate the ability of horses (Equus caballus) to distinguish between the body odour samples of unfamiliar conspecifics. To pick up body odour, we rubbed material on the coat of horses and presented these unknown body odours to 16 different conspecifics of the same sex and similar age. The test consisted of two successive two-min presentations of a sample from one individual (e.g. individual ‘A’) and a simultaneous presentation of samples from individual ‘A’ and a novel individual (e.g. individual ‘B’) during a final third presentation. The results showed that horses, regardless of sex, decreased the time they spent investigating conspecific body odour across the initial two presentations—demonstrating habituation. In the final presentation, the results demonstrated successful discrimination of the previously experienced odour because horses investigated the novel olfactory sample (‘B’) significantly more than the pre-exposed sample (‘A’). Taken together, these findings suggest, for the first time, that horses are able to discriminate two stimuli derived from body odours of unfamiliar conspecifics over short period of time.

Abstract: Contraception is often considered for population control of wildlife that is otherwise protected from more traditional management strategies, though little is known about the behavioral consequences of contraception in wild populations of socially complex animals. Feral horses, Equus caballus, in the western United States are ideal candidates for contraceptive management due to broad scale federal protection, reported herd growth rates of 15-25% per year, and finite public land allocated for them. We investigated influences of the immunocontraceptive porcine zona pellucida (PZP) on social behavior within bands of feral horses in three discrete populations for 4 years. Each band consisted of a single stallion and a harem of adult females (>1 years old) and their foals, as well as associated yearling males and females. Four mutually exclusive behaviors (herding, reproductive, harem tending, and agonism) were analyzed to investigate the difference between behaviors initiated by band stallions toward control mares and contracepted mares within the bands. Additionally, spatial relationships between each stallion and each harem female were analyzed to assess possible passive interactions. A candidate set of 22 hierarchical mixed effects models, using the discrete populations as a random effect on various fixed effects, was analyzed by restricted maximum likelihood estimation. The most supported models were selected by corrected Akaike"s Information Criteria (AICc). Analyses were done on 3 female age cohorts based on distinct fecundity rates: 2 to 5 year olds, 6 to 14 year olds, and > 14 year olds. Stallions herded control mares in the 6 to 14 year cohort more than contracepted mares (n=128, P=0.037) with treatment being the most supported effect, but foal presence (dependent foal) also contributed significantly to the model. Contracepted mares received more reproductive behaviors than control mares in the 6 to 14 year cohort (n = 151, P=0.020). No differences were detected in herding or reproductive behaviors in
the least fecund groups, the 2 to 5 year olds and &#8805; 15 year olds. The only independent variable in the most supported model for reproductive behavior was treatment, and the covariates of foal presence, band residence (resident or transient female), band size, and body condition did not contribute. There were no differences in any age cohort for harem tending or agonism. Spatially, stallions maintained closer relationships with 2 to 5 year old contracepted females than with the same age control females (n=136, P < 0.001) while the group was feeding (at its most dispersed structure), but there were no differences while the band was resting or in locomotion. There were no spatial differences detected in the other age cohorts. Given the polyestrous nature and high fecundity of feral horses, the observed difference in reproductive behaviors between treatment groups was not surprising; however, the difference detected in herding rates was an unexpected behavioral modification. This change in herding behavior suggests that further investigation is needed to determine if PZP immunocontraception has an underlying influence on mare social rank, band structure, and band stability, as well as the scope and long-term importance of these behavioral dynamics.

Abstract: Among mammals, lactation is the most energy demanding part of parental care and so parentoffspring conflict should arise over milk provided by the mother. Mother and offspring should disagree over the length and amount of the milk provision. We focused on effect of pregnancy on suckling behaviour variables as indicators of mother-offspring conflict in domestic horses. We presumed shorter suckling bouts and higher rates of rejected and/or terminated suckling in pregnant mares compared to non-pregnant ones. Increasing conflict over amount of maternal investment between mother and her young are to be expected because of her parallel investment into a nursed foal and a foetus. Eight groups of loose housed lactating mares with foals of Kladruby horse were studied at the National Stud Kladruby nad Labem (Czech Republic) from deliveries to abrupt weaning (at the age of 127 to 210 days). We recorded 10 848 suckling solicitations of 79 mare-foal pairs, from which 10 607 resulted in a suckling bout. In 41 cases a nursing mare became pregnant during lactation. We found no significant effect of pregnancy either on probability of the mother rejecting suckling solicitation of her foal or probability that she terminated a suckling bout. However the overall effect of mother’s pregnancy on suckling bout duration was not significant, there were considerable differences in pregnant and non-pregnant mares according to who terminated a suckling bout, whether the mother or the foal (F(1, 9776) = 12.1, P < 0.001). In case it was the mother then the suckling bout was longer if she was pregnant (65.36 ± 1.25 s) than barren (60.55 ± 1.36 s). We found no impact of pregnancy on duration of suckling bouts terminated by the foal. Further, nursing a foal during the first two trimesters of pregnancy had no negative impact on birth weight of the foetus. In conclusion, we found not higher, but a lower mother-offspring conflict in pregnant than in non-pregnant lactating mares while expecting just the opposite. We suggest that pregnant mares compensate their nursed foals during intensive stages of lactation through a relaxed mother-offspring conflict for later decrease in investment due to increasing demands of the foetus and/or for the shorter period of milk supply. Our results (partly published in Bartosova et al. 2011, PLoS ONE 6(8): e22068) are of high importance in horse breeding. One of the main arguments for early weaning of the foals is regeneration of their pregnant mothers before upcoming delivery. Here we present evidence that a pregnant mare “counts” with her dual maternal investment and “employs” evolutionary mechanisms enabling her to rear a vital foetus. From this point of view there is no objective reason for stressful weaning of her nursed offspring practised in conventional breeding. Supported by AWIN, EU FP7 project No. 266213.

Abstract: Artificial weaning is associated with various stresses for the foal, such as loss of the mother, feeding changes, new and unfamiliar environment, etc. We investigated the impact of two different methods of abrupt weaning on weight gain in group housed Kladruby horses born 2009 (National Stud Kladruby nad Labem, CZ). Two groups of the foals were weaned abruptly at age from 5,5 to 8 months and transported to the other facility but the first group (G1, N=14) spent one week in their home environment after their mothers were led away. The other foals (G2, N=15) were moved away immediately after separation from the mothers (i.e. they lost the mother and known environment at one time). Foals were weighed: at the weaning day, weekly within the first month and then monthly up to 6 months after weaning. Neither birth nor weaning weight differed significantly between the two groups kept under similar nutrition. We hypothesised that a week spent in the home environment should reduce foal’s weight loss usually following the loss of the mother and moving to the unknown environment. The weaning type significantly influenced weight gain the foals reached one week after weaning (p < 0.001, GLM, PROC GLM, SAS). Contrary to our expectations, G1 foals lost their weight whereas G2 ones gained weight during the same period (-4.9 vs. +3.2 kg). G1 foals reached back their weaning weight within 3 weeks after weaning. The weight of the foals at 6 months after weaning was still marginally higher in G2 than G1foals (388.2 vs. 365.7 kg, p < 0.07). We found lower detrimental effect on weight gain in G2 foals (i.e. weaned and immediately moved) compared to G1 foals (weaned and stayed before moved). Thus, our results indicate lower stress induced to the foals in more radical type of weaning. Supported by AWIN, EU FP7 project No. 266213.