Free Choice Experiment Research Articles

Choosing a bigger opponent: the path to victory and greater gains for the small contestant

Animals often engage in contests over limited resources. The probability of winning a contest is primarily determined by the individual's fighting ability relative to its opponent and the perceived value of the disputed resource. Individuals of the hermit crab Calcinus californiensis frequently fight over gastropod shells. We conducted a free-choice experiment to assess the factors that determine individuals’ choice of opponent, contest initiation, and contest resolution. We placed hermit crabs occupying two shell species into a large container and monitored agonistic interactions between crabs. We assessed the asymmetries in fighting ability based on the differences in body mass between the opponents. The shell species and fit (i.e., shell size relative to crab body size) were used as measures of the objective and subjective resource value, respectively. Motivation influenced contest initiation; the crabs occupying too-tight shells were more likely to initiate a contest than the ones in looser-fitting shells. In most cases, the attackers fought for a shell with a looser fit, even if that meant losing a tighter-fitting shell of the preferred shell species. The fighting success for attackers was positively associated with the number of bouts of rapping and the shell size improvement. However, success was negatively correlated with body size asymmetry; attackers that chose opponents larger than themselves were more likely to evict their opponent than the attackers that chose opponents that were smaller. Experimental designs that allow animals to select their own opponents, rather than assigning specific opponents, can strongly contribute to knowledge of agonistic interactions.Significance statementFighting dynamics are commonly assessed by estimating the influence of the resource-holding potential and resource value in pair-matched opponents. Here, however, we examined the influence of asymmetries in resource-holding potential and the objective and subjective value of gastropod shells on the choice of a contender and contest resolution through a free-choice opponent experiment in hermit crabs. The contest initiation was driven by the motivation to obtain a better gastropod shell species or one with a better size fit—factors which are known to improve individual fitness. Furthermore, fighting success was associated with an individual's persistence in displaying aggressive behaviors and its motivation to obtain a better resource. However, contrary to the predictions of game theoretical models, fighting success was higher when attackers chose opponents larger than themselves. Our results highlight the relevance of assessing fighting under more natural conditions by allowing animals to select their opponents.

Hay preferences in horses versus selection by their owners

The objective of the present study was to evaluate the differences in the selection behaviour by horses and by their owners given a choice of three hay types differing in chemical and nutritional composition. Horse groups included 12 French mountain (FM) stallions, 12 Icelandic (IS) and 12 warmblood horses (WB), with the latter groups consisting of mares and geldings. Hays were offered in a free choice experiment over a period of six consecutive days (baseline choice on day 1, adaption period from day 2–5 and a final preference test on day 6). Additionally, the owners of the horses selected among the three hay types, the one which they assumed would best meet their horse's assumed nutritional requirements. Hay types (A, B and C) showed distinct characteristics based on colour, texture morphology and odour and nutrient contents. The latter were analysed with near-infrared spectroscopy. Most horses (69%) preferred hay type B and 31% preferred hay type C, while horses completely avoided hay type A. The group of FM horses exclusively preferred hay B on both test days, the groups of IS and WB horses also showed a preference for hay B, but less pronounced than FM horses choosing both between hay B and C, respectively. Horses did not choose randomly among the hays offered (P < 0.05). In addition, the horses hay preference was influenced by their group assignment (P < 0.05) which, however, cannot be generalized to breed or gender (mares, stallions or geldings). The content of crude protein (r = 0.68), and leaves (r = 0.48) of the hay was positively correlated with the preference of the horses for that particular hay type, although correlations were moderate. Among the owners, 42% chose hay type A, which was completely avoided by the horses, while approximately 30% of the owners chose either hay type B or C, which were richer in energy and protein as the best hay quality for their horses assumed nutritional requirements. Therefore, no significant correlation could be observed between the choice preference of the horses and the selection by the owners. The distinct preference for energy- and protein-rich hay of horses underlines the importance for owners to carefully adjust the hay quality to the horse's activity level and requirements. For horses with lower energy requirements, omission of concentrate feeds, while providing roughage only diets by mixing different hays qualities, appears suitable.

Prey stage preference and functional response of Orius albidipennis (Hetetroptera, Anthocoridae) to Aphis fabae (Homomoptera, Aphididae)

The black been aphid, Aphis fabae Scopoli (Homoptera: Aphididae), is an important pest of many garden, vegetable and ornamental plants in the world. To evaluate Orius albidipennis potential for biological control of the aphid, prey stage preference of the predator to different life stages of the aphid and functional responses of it to different densities of the most preferred life stage were studied under laboratory conditions. Free choice experiment was conducted for evaluation of the bug prey preference between different instar nymphs and wingless female adults of A. fabae. In functional response trials, densities of 5, 10, 15, 20, 25 and 30 s instar nymphs, as the most preferred life stage, per arena were exposed to male and female of the predatory bug for 24-h period. The logistic regression analysis and Roger’s model were used for determinate the type and the parameters of predator’s functional response, respectively. The results showed that O. albidipennis preferred first and second instar nymphs of the aphid in comparison with other life stages. Both sexes of O. albidipennis showed the type II functional response to different densities of the nymphs. The handling times (Th) of O. albidipennis female and male were 1.344 and 1.584 h, respectively. The attack rate value (a) of the female and male bugs were 0.0839 and 1.4814 h−1, respectively. No significant differences were observed between the calculated Th and a for the female and male bugs. From the findings of this study, O. albidipennis can be used in biological control program of A. fabae.

Gas production kinetics and in vitro degradability of tannin-containing legumes, alfalfa and their mixtures

The aim of this study was to determine in vitro ruminal degradability and gas production kinetics of sainfoin (Onobrichis viciifolia; SF), birdsfoot trefoil (Lotus corniculatus; BFT), alfalfa (Medicago sativa L.; ALF) and their binary or trinary mixtures using the gas production technique. The proportions in the mixtures represented: (1) those selected by lambs in a free-choice experiment (70:30 and 50:35:15 ratios for binary and trinary combinations, respectively), or (2) equal proportions (50:50 or 33:33:33 ratios for binary or trinary mixtures, respectively). Organic matter digestibility was greater in ALF and BFT than in SF (0.791 and 0.796 vs 0.751; P < 0.05) and this variable decreased as the proportion of SF in the binary mixtures increased. ALF showed greater (P < 0.05) gas production rates (RMax = 17.7 ml h−1) than BFT (16.5 ml h−1) or SF (12.9 ml h−1), reaching half of the asymptote of gas production (Parameter B = 7.3, 7.0 and 9.5 h, respectively) and maximum gas production rates at earlier times (2.4, 2.6 and 3.0 h, respectively; P < 0.05). The potential gas production (Parameter A) was ALF (210.6 ml) > SF (198.3 ml) > BFT (187.6 ml) (P < 0.05), and gas production rates decreased relative to pure ALF as the proportions of SF or BFT increased in the mixtures (P < 0.05). The presence of two or three species in the substrate did not lead to positive associative effects. Nevertheless, lambs’ preferred mixtures exhibited greater gas production rates and lower times to reach half potential gas production than mixtures formed with equal parts of each of the species (P < 0.05). Thus, mixing alfalfa with sainfoin and/or birdsfoot trefoil in a diet at a 70:30 ratio may allow sheep to maintain fermentability values as high as pure alfalfa while ingesting a diverse diet with some bioactives (e.g., condensed tannins) that provide benefits to the internal environment such as reduced bloat and ammonia formation in the rumen, as well as advantages related to dietary diversity in generalist herbivores like improvements in food intake due to reductions in sensory-specific satiety.

Sense of agency is modulated by interactions between action choice, outcome valence, and predictability

Sense of agency is a feeling of control over one’s actions to cause sensory events in one’s environment. While previous studies investigated the role of action choice and emotional valence of action outcome in forming implicit agency, the results were not consistent and the relationship between these factors remains unclear. We manipulated both action alternatives available and emotional valences of sounds (either positive or negative) as action outcomes and measured the resultant intentional binding effects in two experiments that differed in predictability of outcome valence. When participants could not predict the valence of action outcomes, they showed stronger sense of agency for negative outcomes determined by their free choice (Experiment 1). Conversely, when participants’ actions caused only outcomes with specific valence, this interaction was not observed (Experiment 2). These findings imply that the implicit processes of agency reflect an integrative context-dependent cognition of consequence of action choice, prior to explicit attribution judgments.

Experimentally quantifying the effect of nest-site depth on the predation risk and breeding success of Blue Tits

Predation is a key factor in the nesting preferences of birds. Studies indicate that cavity-breeding birds prefer deeper nest sites, possibly because they are more safe from predation. We studied the Blue Tit (Cyanistes caeruleus), a cavity-breeding passerine, to test (1) whether nest-site depth affects breeding success and (2) whether potential effects of nest-site depth on breeding success are related to predation risk. We performed 2 experiments to separate effects of nest-box depth from potential effects of the quality of the breeding pair. In the first (free-choice) experiment, Blue Tits competed for scarce deep nest boxes that were provided well before nest-box choice, enabling an association between nest-box quality and bird quality. In the second (forced-choice) experiment, we randomly altered nest-box depth after Blue Tits had chosen a nest box, thus disconnecting the association between nest-box quality and bird quality. We found no evidence that the occurrence of signs of predation was related to nest-box depth. However, we did find clear positive effects of nest-box depth (1) on clutch size and hatching success throughout the study area and (2) on fledging success, the number of fledglings, and the overall probability of nest success, specifically in parts of the study area with high predation. We found no indication of independent effects of parental quality on breeding success. Parents also seemed to perceive the shallower boxes as more risky; in shallower boxes, nest thickness was decreased, irrespective of the local predation pressure during the free-choice experiment. Parents nesting in shallow boxes may have had lower breeding success because of (1) increased actual (but undetected) predation and (2) reduced reproductive investment by parents, based on the latter's experience with predation or an evolutionary response to past predation risk.

Dissociating decision strategies in free-choice tasks – A mouse tracking analysis

Everyday life offers a variety of possible actions, from which we choose one that corresponds to our intended goals. How do these goals and actions interact within the mind? One way to investigate this question is free-choice tasks, where participants freely choose the action they want to perform on any given trial. Such tasks are used in research on voluntary actions and goal-driven behavior, such as ideomotor theory. However, these tasks leave participants with a substantial amount of freedom and allow for different response strategies. Such strategies can, though being hidden in the final data, influence the results, for example by hiding the effects of manipulations of interest. To better understand participants' behavior in free-choice tasks, we used mouse tracking in an ideomotor free-choice experiment, where participants learn the connection between an action and an effect. Subsequently, they have to freely choose between actions, while the former effect is presented as a stimulus. We identified two distinct groups that applied different decision strategies. The first group made the decision at the beginning of or before the trial, irrespective of the yet to be presented effect stimulus. The second group decided within the trial and was affected by the stimulus more often. This suggests that people handle free-choice tasks differently which is expressed in heterogeneous choice patterns and response times and an underestimation of the examined effects. These differences potentially limit the reliability of inferences from free-choice experiments and should be considered in the interpretation of their results.

Morphology and glucosinolate profiles of chimeric Brassica and the responses of Bemisia tabaci in host selection, oviposition and development

Plant structures and chemicals, which are developed from the shoot apical meristem (SAM), form the main barriers to insect feeding. A plant chimera containing cells of different genetic origins in the SAM will be morphologically and chemically different compared with the parents and thus may result in differential resistance to herbivores. In this study, we explore if particular elements of plant resistance are localized in one of the layers of SAM; the replacement of one cell layer in a chimera may be linked to change of a single resistance trait to herbivores. The morphology and glucosinolate profiles of two periclinal chimeras (labeled as TTC and TCC, respectively) and grafted parents tuber mustard (labeled as TTT) and red cabbage (labeled as CCC) were compared and the performance of whitefly (Bemisia tabaci) in host selection, oviposition preference and development were assessed under controlled conditions. Both chimeras possessed leaf trichomes as parent tuber mustard TTT, however, TTC had significantly more trichomes than TCC and parent TTT. Leaf wax content of both chimeras was intermediate between the two parents. Five aliphatic and two indole glucosinolates were detected in both chimeras, whereas three aliphatic glucosinolates (3-methyl-sulfinylpropyl, 4-methyl-sulfinylbutyl and 2-hydroxy-3-butenyl) were not detected in tuber mustard, and one aliphatic glucosinolate (3-butenyl) was not detected in red cabbage. Unexpectedly for a chimera, the quantities of two aliphatic glucosinolates (3-methyl-sulfinylpropyl and 4-methyl-sulfinylbutyl) in both TTC and TCC were 3- to 5-fold higher than parents. In olfactory preference assays, B. tabaci showed preference to CCC, followed by TCC, TTC and TTT, and number of eggs laid showed the same pattern: CCC>TCC>TTC>TTT. Interestingly, more whiteflies landed on TTT plants than the other three types in a free choice experiment and the developmental duration from egg to adult was the shortest on TTT and increased in the order TTT<TTC<TCC<CCC. Our results indicate plant defenses traits of leaf waxes, trichomes and glucosinolates are not controlled by one cell layer of SAM, but are influenced by interactions amongst cell layers. The overall findings suggest that periclinal chimera systems can be a valuable approach for the study of plant-insect interactions and may also be useful for future resistance breeding.

Barren diets increase wakeful inactivity in calves

Inactivity is a vastly understudied behavioural category, which may reflect positive or negative affective states in captive or domesticated animals. Increased inactivity in barren-housed animals, in combination with an increased or decreased interest in stimuli, e.g. novel objects, can indicate boredom or apathy. Another theory is that inactivity is an alternative strategy to stereotypies to cope with sub-optimal conditions. The aim of this study was to further our understanding of inactive behaviours and possible associated negative affective states in intensively raised calves fed different diets. In two separate experiments, Holstein-Friesian veal calves (N=40+160) were fed barren or enriched diets: 1) imposed/restricted diet versus free dietary choice (experiment 1); 2) no additional straw versus ad libitum provision of straw (experiment 2); 3) low versus high solid feed provision (experiment 2); 4) bucket versus automated milk dispenser for milk replacer feeding, with high or low solid feed provision (experiment 2). Inactive behaviours, i.e. experiment 1: lie, idle and sleep; experiment 2: lie idle, stand idle, and sleep, were recorded at two ages (experiment 1: 12 and 26wk; experiment 2: 15 and 24wk) using instantaneous scan sampling. In experiment 2, latency to touch two novel objects was recorded at 15 and 24wk. No differences in inactivity were found between calves with a restricted or free choice diet (experiment 1). However, calves fed the more barren diets in experiment 2 showed more lying idle at 24wk of age, and calves with no ad libitum straw in particular, showed more standing idle at 24wk of age (P<0.05). No differences in latency to touch the novel objects were found. Therefore, although barren diets were generally associated with higher levels of inactivity, we found no support that this inactivity reflected boredom or apathy. Only weak associations were found between inactivity and stereotypies, providing only limited support for the idea that these constitute alternative strategies to cope with sub-optimal conditions.

Neural evidence for the intrinsic value of action as motivation for behavior

The intrinsic value of an action refers to the inherent sense that experiencing a behavior is enjoyable even if it has no explicit outcome. Previous research has suggested that a common valuation mechanism within the reward network may be responsible for processing the intrinsic value of achieving both the outcome and external rewards. However, how the intrinsic value of action is neurally represented remains unknown. We hypothesized that the intrinsic value of action is determined by an action-outcome contingency indicating the behavior is controllable and that the outcome of the action can be evaluated by this feedback. Consequently, the reward network should be activated, reflecting the generation of the intrinsic value of action. To test this hypothesis, we conducted a functional magnetic resonance imaging (fMRI) investigation of a stopwatch game in which the action-outcome contingency was manipulated. This experiment involved 36 healthy volunteers and four versions of a stopwatch game that manipulated controllability (the feeling that participants were controlling the stopwatch themselves) and outcome (a signal allowing participants to see the result of their action). A free-choice experiment was administered after the fMRI to explore preference levels for each game. The results showed that the stopwatch game with the action-outcome contingency evoked a greater degree of enjoyment because the participants chose this condition over those that lacked such a contingency. The ventral striatum and midbrain were activated only when action-outcome contingency was present. Thus, the intrinsic value of action was represented by an increase in ventral striatal and midbrain activation.

Evaluating the feeding preferences of West Nile virus mosquito vectors using bird-baited traps.

BackgroundThe total contact rates (TCRs) between mosquito vectors and their potential hosts have a serious impact on disease transmission dynamics. Culex pipiens (sensu stricto) (s.s.) is considered the main vector of the West Nile Virus (WNV) in Europe and birds are the reservoir hosts. The results of our previous study showed that WNV seroreactors are significantly more prevalent among raptors compared to a range of other wild avian groups. The current study aims to assess the role of bird type (raptor vs others) and bird size on mosquito feeding preferences in a free-choice experiment using bird-baited traps.MethodsFrom July to September 2014, a battery of six bird-baited traps was operated in twelve mosquito capture sessions. Eight bird species, belonging to five different orders, including raptors, were used. After each session, the trapped mosquitoes were collected and identified using standard keys. Two sets of independent generalized linear mixed models (GLMM) were used to assess mosquito vector feeding preferences (MFp) among different bird species and types.ResultsA total of 304 mosquitoes belonging to seven taxa were collected, C. pipiens being by far the most abundant (84.2 % of the total mosquito catch). Most C. pipiens were engorged (83.59 %). The selected model showed that 25.6 % of the observed variability of MFp is explained by the interaction between bird size and bird type, with C. pipiens preferring to feed on large birds, especially raptors. The proportion of engorged mosquitoes was 1.9-fold higher in large (22.88 %; range 0–42 %) than in medium-sized raptors (11.71 %; range 0–33 %), and was nearly the same in medium-sized (9.08 %; range 0–26 %) and large (8.5 %; 6–24 %) non-raptor species.ConclusionCulex pipiens showed an obvious preference for large raptors, which concurs with the higher seroprevalence to WNV in our previous study. The appreciable feeding by C. pipiens on large raptors makes them useful alternative sentinels to poultry for WNV surveillance. Thus, wildlife parks and rehabilitation centers can contribute to surveillance efforts to a greater extent.

Ketertarikan Anaxipha longipennis Serville (Orthoptera: Gryllidae) terhadap Beberapa Jenis Gulma di Sawah sebagai Tempat Bertelur

Jengkerik Anaxipha longipennis Serville (Orthoptera: Gryllidae) adalah salah satu predator generalis di habitat sawah yang menyukai telur pelipat daun padi dan serangga-serangga kecil lain seperti wereng-wereng padi. Jengkerik betina menyisipkan telurnya pada batang atau pelepah daun padi dan gulma-gulma di habitat sawah. Tempat bertelur yang disukai akan menjamin keberlanjutan keberadaan jengkerik di habitat sawah. Pada penelitian ini telah dicoba untuk mengetahui jenis gulma yang dipilih sebagai tempat bertelur selain pada tanaman padi. Tujuh belas species gulma dan padi telah dipaparkan pada 5 pasang jengkerik sebagai tempat bertelur pada suatu percobaan memilih secara bebas. Sembilan spesies gulma telah dipilih sebagai tempat bertelur oleh A. longipennis selain padi. Telur diletakkan paling banyak pada padi dan berturut-turut diikuti pada Monochoria vaginalis, Cyperus rotundus, C. iria, Echinochloa colonum, E. crusgalli, Eleusine indica, Fimbristylis miliacea, Imperata cylindrica, dan Limnocharis flava. Sedangkan Alternanthera sessilis, Ludwigia adscen-dens, Commelina diffusa, Leersia hexandra, Leptochloa chinensis, P. repens, Ageratum conyzoides dan Sonchus arvensis tidak dipilih oleh A. longipennis sebagai tempat bertelur.

The psychophysics of uneconomical choice: non-linear reward evaluation by a nectar feeder

Uneconomical choices by humans or animals that evaluate reward options challenge the expectation that decision-makers always maximize the return currency. One possible explanation for such deviations from optimality is that the ability to sense differences in physical value between available alternatives is constrained by the sensory and cognitive processes for encoding profitability. In this study, we investigated the capacity of a nectarivorous bat species (Glossophaga commissarisi) to discriminate between sugar solutions with different concentrations. We conducted a two-alternative free-choice experiment on a population of wild electronically tagged bats foraging at an array of computer-automated artificial flowers that recorded individual choices. We used a Bayesian approach to fit individual psychometric functions, relating the strength of preferring the higher concentration option to the intensity of the presented stimulus. Psychometric analysis revealed that discrimination ability increases non-linearly with respect to intensity. We combined this result with a previous psychometric analysis of volume perception. Our theoretical analysis of choice for rewards that vary in two quality dimensions revealed regions of parameter combinations where uneconomic choice is expected. Discrimination ability may be constrained by non-linear perceptual and cognitive encoding processes that result in uneconomical choice.

How choice affects and reflects preferences: Revisiting the free-choice paradigm.

After making a choice between 2 objects, people reevaluate their chosen item more positively and their rejected item more negatively (i.e., they spread the alternatives). Since Brehm's (1956) initial free-choice experiment, psychologists have interpreted the spreading of alternatives as evidence for choice-induced attitude change. It is widely assumed to occur because choosing creates cognitive dissonance, which is then reduced through rationalization. In this article, we express concern with this interpretation, noting that the free-choice paradigm (FCP) will produce spreading, even if people's attitudes remain unchanged. Specifically, if people's ratings/rankings are an imperfect measure of their preferences and their choices are at least partially guided by their preferences, then the FCP will measure spreading, even if people's preferences remain perfectly stable. We show this, first by proving a mathematical theorem that identifies a set of conditions under which the FCP will measure spreading, even absent attitude change. We then experimentally demonstrate that these conditions appear to hold and that the FCP measures a spread of alternatives, even when this spreading cannot have been caused by choice. We discuss how the problem we identify applies to the basic FCP paradigm as well as to all variants that examine moderators and mediators of spreading. The results suggest a reassessment of the free-choice paradigm and, perhaps, the conclusions that have been drawn from it.

Experimental paradigm influence subject’s perception of attitudes

Japanese utterances spoken with different attitudes (admiration, suspicion, and disappointment) were independently manipulated for pitch-contour and voice quality using STRAIGHT {Kawahara}. Close copy stylization of the prototypical pitch contour for the three attitudes was imposed on the naturally spoken utterances, producing stimuli with all combinations of voice quality types and pitch-contour shapes. The utterances were submitted to two separate experiments, wherein subjects were asked to judge the attitude of the morphed utterances. The first, a forced choice experiment, asked subjects to choose if the utterances were admiration, suspicion, or disappointment, and the second, a free choice experiment, where subjects could freely choose the attitude they perceived. The results from the forced choice test indicated that subjects used pitch contour cues to choose speaker attitude. However, the results from the free choice paradigm indicated that subjects used both voice quality and intonation cues, and were able to perceive more affect types than the original three. Whereas the forced choice paradigm suggested that intonation was the primary cue for listeners to determine speaker attitudes, the free choice paradigm suggested an independence of voice quality and intonation in determining speaker attitudes, which resulted in a larger number of perceived attitudes by listeners.

Individual differences in novelty-seeking behavior but not in anxiety response to a new environment can predict nicotine consumption in adolescent C57BL/6 mice

Considering that adolescence is associated with an increased motivation to seek out new stimuli and with low anxiety levels in exploring novel environments, and that both behavioral traits may be associated with substance abuse, we investigated whether the behavioral response to a novel environment can predict subsequent oral nicotine self-administration in adolescent C57BL/6 mice. On postnatal day 30 (PN30), the novelty-seeking behavior and anxiety levels were assessed in a hole board activity box. The total number of head-dips (DIP) was used to classify animals either into the high novelty (HN; DIP above median) or low novelty (LN; DIP below median) groups. The percentage of center squares crossed (CEN) was used to classify animals either into the high anxiety (HA; CEN below median) or low anxiety (LA; CEN above median) groups. From PN31 to PN41, all animals were given a free choice between tap water or a nicotine solution (10 μg/ml). LN mice did not change nicotine intake throughout the free choice procedure, however, HN mice presented a marked increase in consumption. There were no differences in consumption between HA and LA mice. Our results indicated that mice that presented a more intense novelty-seeking behavior increased their preference for nicotine during the free choice experiment but that anxiety levels did not predict nicotine consumption. These results suggest that higher motivation to seek out new experiences is a significant contributor to drug use in adolescents and that anxiety is probably not a major factor that determines differential nicotine consumption during adolescence.

Avoidance of atmospheric ammonia by domestic fowl and the effect of early experience

An experiment was carried out to determine if broiler fowl, when given a free choice, would avoid ammoniated environments. The effect of rearing aerial environment on these preferences was tested subsequently during a similar free choice experiment. Firstly, each of four flocks of twelve 26-day-old female Ross broiler fowl, reared in fresh air, was placed in a preference chamber with access to four compartments. After an initial 4-day acclimatisation period, where no ammonia was provided, birds were given a free choice of 4, 11, 20 and 37 ppm atmospheric ammonia over a period of 16 days. Coloured panels in each of the compartments provided the birds with a secondary cue to associate with aerial environment. Ammonia/colour cue treatment was relocated to a different compartment every 4 days. Data collection occurred during two periods that differed in light level: bright (100 lx) and dim (10 lx). The birds avoided the two higher ammonia concentrations, choosing to spend equal amounts of their time in 4 and 11 ppm during the bright phase. During the dim period, broiler fowl spent significantly more time in 4 ppm (light intensity and ammonia occupancy interaction: F 3,60 = 5.40; P = 0.002). Ammonia significantly affected compartment visit duration with back transformed mean visits of 37, 28, 20 and 15 min for 4, 11, 20 and 37 ppm, respectively (Wald statistic = 29.07; d.f. = 3; P < 0.001). Secondly, eight flocks of 12 female broiler fowl were exposed to either 2 or 19 ppm ammonia from 1 to 26 days of age. At 26 days, each flocks, was placed in a preference chamber with access to four compartments and kept at the same atmospheric ammonia concentration (2 or 19 ppm) during an acclimatisation periods of 4 days. Following acclimatisation, a 4-day test was conducted in which the birds were given a choice of compartments containing 4, 12, 20 and 37 ppm ammonia with colour cues. Birds again avoided the two higher ammonia concentrations ( F 3,15 = 8.54; P = 0.002) and there was no significant interaction between ammonia and previous exposure. Again there was an effect of ammonia on compartment visit duration (Wald statistic = 15.94; d.f. = 3; P = 0.001) but there was no significant interaction between ammonia and previous exposure. Broiler fowl avoid ammonia at concentrations commonly found on poultry units regardless of previous experience, suggesting it to be aversive at concentrations above approximately 10 ppm.

Preferences of growing ducklings and turkey poults for illuminance

AbstractThe illuminance and spectral power distribution in 19 duckling and 16 turkey poult houses in the UK were sampled. Illuminance was highly variable within duckling houses and to a lesser extent in housing for turkey poults. In a free choice experiment, the preferences of commercial ducklings and turkey poults for four incandescent illuminances (&lt;I, 6, 20 and 200 Ix; Osram, 60 W, Pearl) were tested at 2 and 6 weeks of age. Four replicate flocks of 12 birds were given continuous access to four compartments illuminated with each illuminance for six days. The illuminances were changed daily between the compartments. After two days of conditioning, the birds’ location and behaviour was recorded at 10 min intervals over 22 h. Nine and 12 defined behavioural categories were recorded for the ducklings and poults respectively. Ducklings spent significantly more time occupying the three brightest light environments both at 2 and 6 weeks of age, and the least time in the dimmest. Illuminance had a significant effect on the partition of behaviours amongst the light environments. At 2 weeks of age, locomotion and environmentally directed pecking occurred most often in 6, 20 and 200 lx, whereas at 6 weeks, preening and feeding also occurred more often in these light environments. At 6 weeks of age, resting, standing and drinking occurred significantly more often in 6 lx than in the dimmest environment. Turkeys spent most time in the brightest environment at 2 weeks of age, but in 20 and 200 Ix at 6 weeks. This change in overall preference was reflected in the partition of different behaviours between the light environments. At 2 weeks of age, all behaviours were observed to occur most often in 200 lx. At 6 weeks, resting and perching were observed least often in &lt;I lx, whereas all other activities were observed more in the two brightest light environments. These results show that ducklings and turkey poults have significant but differing preferences for illuminance, and imply that some spatial or temporal variation in the ambient illuminance of housing would be consistent with their preferences.

Female American mink, Mustela vison, mate multiply in a free-choice environment

Like most solitary carnivores, the home ranges of male American mink overlap with those of several females, but each female typically shares its range with only a single male. Nevertheless, female mink produce multiply sired litters. Unusually among mammals, the physiological characteristics of female American mink make them highly suited to multiple paternity, suggesting that polyandry in the species may result from female behaviour rather than from coercion by males. In a free-choice experiment on captive-bred animals, all female mink mated multiply, with seven of the eight mating with all three available partners. Since females sometimes resisted copulations, multiple mating in this species may result from their behaviour rather than male coercion. Females visited males nonrandomly, but visiting patterns did not predict mating patterns, suggesting disparate social and mating preferences. There was no evidence for precopulatory female choice, since the allocation of copulations among available males did not deviate significantly from the expected distribution. Females mated multiply only around the predicted times of ovulation, contrary to the expectation that they should be more selective at times of peak fertility. Larger males copulated for longer in total: copulation duration is probably under male control, suggesting that larger males could influence mating duration, perhaps increasing their share of paternity by greater sperm transfer. Our observations suggest that in wild populations, mating patterns could be influenced by female preference for multiple partners.

Preferences of growing ducklings and turkey poults for illuminance

The illuminance and spectral power distribution in 19 duckling and 16 turkey poult houses in the UK were sampled. Illuminance was highly variable within duckling houses and to a lesser extent in housing for turkey poults. In a free choice experiment, the preferences of commercial ducklings and turkey poults for four incandescent illuminances (