Activity, social and sexual behaviour in Red Junglefowl selected for divergent levels of fear of humans

Social-pair judgment bias testing in slow-growing broiler chickens raised in low- or high-complexity environments

Impacts of environmental complexity on affective states in slow-growing broiler chickens (Gallus gallus domesticus) are unknown. Chickens' performance in judgment bias tests (JBT) can be limited as they are tested individually, causing fear and anxiety. The objectives were to apply a social-pair JBT to assess the effect of environmental complexity on slow-growing broiler chickens` affective states, and assess the impact of fearfulness, anxiety, and chronic stress on JBT performance. Six-hundred Hubbard Redbro broilers were housed in six low-complexity (similar to commercial) or six high-complexity (permanent and temporary enrichments) pens. Twelve chicken pairs were trained (1 pair/pen, n = 24 chickens) using a multimodal approach (visual and spatial cues), with reward and neutral cues of opposing color and location. Three ambiguous cues were tested: near-positive, middle, and near-neutral cues. Approach and pecking behavior were recorded. Eighty-three percent of chickens (20/24) were successfully trained in 13 days. Fearfulness, anxiety, and chronic stress did not impact chickens' performance. Chickens successfully discriminated between cues. Low-complexity chickens approached the middle cue faster than high-complexity chickens, indicating that they were in a more positive affective state. The environmental complexity provided in this study did not improve affective states in slow-growing broiler chickens compared to a control. A social-pair JBT resulted in excellent learning and testing outcomes in slow-growing broilers.

Reproduction in South American wild canids—A review

Canids occupy the top of the food chain and are fundamental in sustaining a wild animal/environmental balance. South America, the most biodiverse continent, has 11 species of canids inhabiting diverse biomes, with or without overlapping territories. Although several species are threatened, little is known about their reproductive biology. Remarkably, basic knowledge regarding ejaculate characteristics, sexual behavior, female reproductive cycles, pregnancy and management, and parturition are scarce or absent. These gaps complicate or preclude development of conservation programs. This review compiles the current knowledge of the reproductive biology of South American canids and discusses implications of this scenario.

Does Observer Presence Modify the Behavior and Enclosure Use of Captive Edwards’ Pheasants?

It is well known that captive animals alter their behavior and space use when observed by visitors, with the concept coined the ‘visitor effect’. The ‘observer effect’, described as any alteration in behavior and enclosure use as a result of a quiet, stationary observer, has been less studied. This study investigates the observer effect in two pairs of Edwards’ pheasants (Lophura edwardsi) and their offspring at Sparsholt College, United Kingdom. The impact of an observer (as opposed to camera) on behavior and enclosure use of pheasants was observed, using instantaneous focal sampling. Enclosure use was measured by converting both enclosures into unequal zones and then assessing the evenness of enclosure use through modified Spread of Participation Index. Poisson regression analysis was used to investigate observer impact, alongside the additional variables of keeper and visitor presence, temperature, and individual bird differences. Overall, the behaviors of resting and clustering were significantly increased during observer presence, whereas feeding and locomotion were significantly decreased. The behaviors of preening and standing were not affected by observer presence, though they were influenced by keeper and visitor presence. Enclosure use was also affected by observer presence, though the effect size was small. This suggests that pheasants may perceive the presence of humans near their enclosures as a potential threat, and may alter their behavior to reduce detection, similar to their wild counterparts. Animal researchers should consider the potential impact of observer presence on their subjects, particularly when observing species such as pheasants.

Selection for Reduced Fear of Humans Changes Intra-Specific Social Behavior in Red Junglefowl—Implications for Chicken Domestication

The domestic fowl has a different social behavior compared to their ancestor, the red junglefowl. To examine whether selection for tameness has affected their intra-specific social behavior, 32 red junglefowl from two selection lines, one selected for increased tameness and one selected for a high fear of humans for ten generations, were kept in a group of two females and two males each and were observed in a semi-natural undisturbed enclosure. Birds selected for a low fear of humans had more social conflict, and the males from this selection crowed more and were more often observed in low social proximity to others. The high-fear birds spent more time close together with the rest of the group and performed more social, non-aggressive pecking. These results are consistent with known differences between ancestral red junglefowl and domesticated laying hens. Our results show that intra-specific social behavior has been affected as a side-effect of selection for increased tameness. This may have interesting implications for the emergence of the domestication syndrome in chickens.

Gut Microbiota Linked with Reduced Fear of Humans in Red Junglefowl Has Implications for Early Domestication

Domestication of animals can lead to profound phenotypic modifications within short evolutionary time periods, and for many species behavioral selection is likely at the forefront of this process. Animal studies have strongly implicated that the gut microbiome plays a major role in host behavior and cognition through the microbiome-gut-brain axis. Consequently, herein, it is hypothesized that host gut microbiota may be one of the earliest phenotypes to change as wild animals were domesticated. Here, the gut microbiome community in two selected lines of red junglefowl that are selected for either high or low fear of humans up to eight generations is examined. Microbiota profiles reveal taxonomic differences in gut bacteria known to produce neuroactive compounds between the two selection lines. Gut-brain module analysis by means of genome-resolved metagenomics identifies enrichment in the microbial synthesis and degradation potential of metabolites associated with fear extinction and reduces anxiety-like behaviors in low fear fowls. In contrast, high fear fowls are enriched in gut-brain modules from the butyrate and glutamate pathways, metabolites associated with fear conditioning. Overall, the results identify differences in the composition and functional potential of the gut microbiota across selection lines that may provide insights into the mechanistic explanations of the domestication process.

Effect of Environmental Complexity and Stocking Density on Fear and Anxiety in Broiler Chickens

Barren housing and high stocking densities may contribute to negative affective states in broiler chickens, reducing their welfare. We investigated the effects of environmental complexity and stocking density on broilers' attention bias (measure of anxiety) and tonic immobility (measure of fear). In Experiment 1, individual birds were tested for attention bias (n = 60) and in Experiment 2, groups of three birds were tested (n = 144). Tonic immobility testing was performed on days 12 and 26 (n = 36) in Experiment 1, and on day 19 (n = 72) in Experiment 2. In Experiment 1, no differences were observed in the attention bias test. In Experiment 2, birds from high-complexity pens began feeding faster and more birds resumed feeding than from low-complexity pens following playback of an alarm call, suggesting that birds housed in the complex environment were less anxious. Furthermore, birds housed in high-density or high-complexity pens had shorter tonic immobility durations on day 12 compared to day 26 in Experiment 1. In Experiment 2, birds from high-density pens had shorter tonic immobility durations than birds housed in low-density pens, which is contrary to expectations. Our results suggest that birds at 3 weeks of age were less fearful under high stocking density conditions than low density conditions. In addition, results indicated that the complex environment improved welfare of broilers through reduced anxiety.

Tameness correlates with domestication related traits in a Red Junglefowl intercross

Early animal domestication may have been driven by selection on tameness. Selection on only tameness can bring about correlated selection responses in other traits, not intentionally selected upon, which may be one cause of the domesticated phenotype. We predicted that genetically reduced fear towards humans in Red Junglefowl, ancestors of domesticated chickens, would be correlated to other traits included in the domesticated phenotype. Fear level was determined by a standardised behaviour test, where the reaction towards an approaching human was recorded. We first selected birds for eight generations for either high or low fear levels in this test, to create two divergent selection lines. An F3 intercross, with birds from the eighth generation as parentals, was generated to study correlations between fear‐of‐human scores and other unselected phenotypes, possibly caused by pleiotropy or linkage. Low fear‐of‐human scores were associated with higher body weight and growth rates, and with increased activity in an open field test, indicating less general fearfulness. In females, low fear‐of‐human scores were also associated with more efficient fear habituation and in males with an increased tendency to emit food calls in a mirror test, indicating increased social dominance. Low fear‐of‐human scores were also associated with smaller brain relative to body weight, and with larger cerebrum relative to total brain weight in females. All these effects are in line with the changes observed in domesticated chickens compared to their ancestors, and we conclude that tameness may have been a driving factor underlying some aspects of the domesticated phenotype.

Rapid behavioral assay using handling test provides breed and sex differences in tameness of chickens

BACKGROUND

Japanese indigenous chicken breeds are often used to improve meat quality rather than broilers in the Jidori industry. There are sometimes severe crowding accidents caused by many birds frightened by environmental stimuli. To prevent the economic loss, the chickens need to be more gentle, tame, and imperturbable.

METHODS

In this study, a new handling test for tameness in adult chickens in individual cages was performed with 100 birds from each sex of Shamo, Rhode Island Red, Nagoya, Australorp, and Ukokkei, as well as 10 hens of F1 hybrid between Shamo and Rhode Island Red, to measure both active and passive tameness. We counted the number heading toward human hands (heading) and retreating in other directions (avoiding) in both active and passive tameness phases, as well as the number of steps taken (step) during the handling test.

RESULTS

Male chickens exhibited higher avoidance behavior than females. Nagoya females displayed the lowest level of avoidance behavior, which implies passive tameness. In terms of active tameness, a variety of phenotypes can be obtained in different combinations of breed and sex. These results suggested the handling test will be good method for rapid screening of individual differences in tameness. In addition, there were heterosis effects on avoidance and locomotive behaviors. Since F1 is often used in the Jidori industry, the breeders should be tested not only for meat production but also for tameness.

CONCLUSIONS

In the future, combining both the behavioral screening and the population genomics will establish typical evidence about mechanisms of tameness and domestication in animals.