Extent of digging and its possible underlying causal factors in penned blue foxes

A recent European animal welfare recommendation stresses the importance of studying digging behaviour in farm-born blue foxes (Alopex lagopus). The current study was conducted (1) to clarify the extent of digging and (2) to evaluate factors that motivate digging. In experiment 1, six juvenile male blue foxes were housed together from August to the following June in an earthen enclosure. Experiment 2 was conducted from July to December, using ten enclosures each containing two juvenile male blue foxes. Behaviour was monitored by 24-h video recordings and visual observations. Progress of digging was also followed by making scale drawings of all digging marks on paper. As early as the first study day, clear signs of digging were observed. Digging sites were concentrated below and close to nestboxes and pen walls. Maximally about 20% of the total enclosure area was affected. The total surface area of digging sites did not increase from late summer onwards because foxes tended simultaneously to cover part of the old sites when digging new ones. Motivational tendency to dig varied with time. Digging activity decreased during autumn and almost totally ceased during winter. In May, foxes resumed digging activity. Digging motivation was evaluated by two means: (1) by analyzing digging purpose (experiments 1 and 2), and (2) by the damming-up test (experiment 1), that is, after 10 months foxes that had been exposed to the earthen floor were transferred for 12 days into wire-mesh cages with no possibility to dig in the ground. Thereafter, foxes were transferred back into the earthen enclosure to measure the rebound of digging following deprivation. Foxes were observed to dig for the following reasons: (1) to make a hole or a resting site, (2) to locate an escape route, (3) to cache food, faeces, or sticks, (4) in response to a novel object (new nestbox, replacement of nestbox), and (5) displacement without any clear goal. Daily time spent digging averaged 7 min and 17 min per fox in Exps. 1 and 2, respectively. A clear rebound effect for digging was not identified. It can be concluded that digging is a complex behavioural pattern caused by a variety of motivations that can vary over time. The present study was unable to show unambiguously that digging is an important need for farmed foxes. Received: 28 February 2000 / Received in revised form: 6 June 2000 / Accepted: 20 June 2000     

Optimal behaviour sampling and autocorrelation curve: modelling data of farmed foxes

Behavioural investigations frequently make use of video recordings. In a typical study, behaviour is recorded during a 24-h period using instantaneous sampling, a method whereby consecutive samples taken from the same animal are autocorrelated. This study sought to model the autocorrelation function and to evaluate the optimal sampling interval for recording periods of different length in farmed blue foxes. The data were based on video recordings. The autocorrelation was found to have two components: short-range and long-range. The range of the short-range component was from 2 to 4 min, implying that an animal continues the same operation without interruption for several minutes. The duration of the long-range component was from 20 to 75 min and was affected by the animals mental state. The optimal sampling interval was not the same for all the behaviours studied and, moreover, depended on the length of the recording period. If the recording period lasted for 3 to 5 days, the optimal sampling interval was from 10 to 15 min; if, however, there was only one recording day, the optimal sampling interval was from 4 to 6 min.     

OEP及卵黄浓度对蓝狐冻融精子质量的影响

人工采取 6只优质芬兰雄性蓝狐精液 ,利用不同OEP及卵黄含量的Tris 果糖 -柠檬酸钠稀释液稀释 ,制成细管冻精 ,透射电镜下观察精子冷冻前后质膜和顶体超微结构 ,荧光免疫方法检测不同培养时间冻融精子的质量。结果表明 ,蓝狐精子顶体外膜双层膜的厚度为 0 0 2 0 μm ,冷冻 -解冻过程中易发生质膜膨胀、顶体外膜融合现象。顶体产生的囊泡分两种类型 ,一种是体积较大的中空囊泡 ,平均直径为 1 2 5 μm。另一种是体积较小的实体囊泡 ,内充满顶体内容物 ,平均直径为 0 83μm ,两种囊泡的数量不定。OEP能有效抑制顶体囊泡形成 ,影响顶体囊泡类型、体积大小及囊泡数量 ,添加适宜剂量OEP能使顶体囊泡的体积明显缩小 ,囊泡的总数及中空囊泡的数量显著降低。蓝狐冻融精子质量与OEP及卵黄剂量有关 ,在卵黄存在的前提下 ,OEP有利于维持冻融过程中质膜 (5 6 3% )、顶体的完整性 (5 7 8% ) ,显著提高冻融精子活力 (5 4 7% )。在蓝狐精液稀释液中 ,OEP、卵黄的适宜含量分别为 1 %、 2 0 %     

Quantitative assessment of the effects of space allowance, group size and floor characteristics on the lying behaviour of growing-finishing pigs

To obtain quantitative information that can be later used in animal welfare modelling, the relationship between the lying behaviour of growing-finishing pigs (initial body weight (BW) between 19 and 87 kg) and different factors related to the housing conditions, with a potential negative effect on their welfare, was studied by means of a meta-analytical approach. Data from 22 experiments reported in 21 scientific publications were collected. The space allowance, expressed on an allometric basis by means of a k-value (m2/BW0.667), the group size (n) and the floor characteristics (fully and partly slatted v. non-slatted floor), as well as their significant two-way interactions were used as fixed effects, and the experiment was used as a random factor to take into account the interexperiment effect. Further regression analyses were performed on the predicted values of observations in order to improve the adjustment of data. A significant quadratic relationship was established between space allowance (k-value, P < 0.05; squared k-value, P < 0.01) and the percentage of time spent lying. A significant interaction between the k-value and the floor type was also found (P < 0.05), showing that the relationship between space allowance and lying behaviour is affected by the presence or absence of slats. Threshold k-values were obtained using broken-line analyses, being about 0.039 for slatted floors and almost double for non-slatted floors. Compared to other studies, these values suggest that the ability to rest as space availability decreases may be compromised before a reduced performance becomes apparent. Group size did not show a significant effect. Additional information should be added to the model, as further data become available, to adjust the proposed parameters as well as to try to include the effect of other important aspects such as that of ambient temperature.     

Effects of space allowance on the grazing behaviour and spacing of sheep

In each of two experiments, four groups of 10 female Scottish Blackface sheep grazed for 2 weeks at each of four space allowances, according to a Greco-Latin Square design. Space allowances were 80, 100, 133 or 200m(2) per head in Experiment 1 and 50, 67, 100 or 200m(2) per head in Experiment 2. Confounding of space allowance and grazing pressure was avoided by the use of a rotational grazing system. Mean distances between sheep were measured from video recordings and distances expected by chance were calculated from simulations in which sheep were located within plot areas using randomly selected co-ordinates.Total time spent grazing was higher at 200m(2) per head and less at 50m(2) per head than at other space allowances, but there was no evidence for an effect of space allowance on herbage intake or digestibility, biting rate or the proportion of grazing time spent in ingestive behaviour. At space allowances from 50 to 133m(2) per head, there were no significant differences between mean observed inter-animal distances and those expected by chance, but observed values were lower than expected values at 200m(2) per head. At all space allowances, mean observed distances between sheep and their nearest neighbours were lower than distances expected by chance.The results show that, on relatively high quality, homogeneous vegetation, female Scottish Blackface sheep will graze at space allowances between 50 and 200m(2) per animal with no evidence of repulsion between individuals and with no clear evidence of grouping until space allowance reaches 200m(2). It is concluded that the relationship between grazing time and space allowance may reflect the extra activity required to maintain group cohesion as space allowance increases.     

The effect of a combination of permanent breeding cage and low housing density on the reproductive success of farmed blue foxes

Social factors are known to affect the reproduction of many canids both in the wild and in farms. For example, reproduction in farmed silver foxes is regulated by social stress; foxes seem to benefit from noncramped housing conditions and permanent breeding cages. However, no comparable studies have been carried out in farmed blue foxes.

The aim of our experiment was to create an alternative, improved, economically viable and practical housing solution for blue foxes. Therefore, we compared reproductive performance of blue foxes in permanent breeding cages with low animal densities (L group, N = 79) and traditional housing with its changing social environment with high animal density (H group, N = 74). The reproductive data from the L and H groups were compared separately for primiparous and multiparous vixens because the reproductive performance in primiparous vixens was substantially lower (P < 0.001) than in multiparous vixens.

Altogether, 41 and 39% of the primiparous vixens in the H and L group whelped (P > 0.05), but only 28 and 34%, respectively, weaned at least one cub (P > 0.05), i.e., 72 and 66% of the primiparous vixens did not reproduce in the H and L group, respectively (P > 0.05). The total reproductive performance, expressed as cubs at weaning per breeding female, was 1.7 ± 3.5 for the H and 1.6 ± 2.9 for the L group (P > 0.05). In the primiparous vixens, the only statistically significant difference observed between the two housing systems was that the onset of oestrus occurred five days earlier in the H than in the L group (P < 0.05).

All multiparous vixens in the L group exhibited oestrus compared to 94% in the H group (P > 0.05). Furthermore, there was a nonsignificant (ns) trend for fewer barren females (9% versus 17%), more successfully reproducing vixens (83% versus 74%) and a higher number of live-born cubs (10.9 ± 4.7 versus 9.4 ± 3.9) in the L than in H group in the multiparous vixens (for all P > 0.05). This resulted in 1.7 and 1.4 cubs more per breeding and per mated vixen, respectively, at weaning in the L group (7.3 ± 5.0) compared to the H group (5.6 ± 4.2), but also this difference was nonsignificant.

Although our present results lack statistical significance, they are promising enough to encourage field experiments with sufficiently large number of animals to prove or disprove these preliminary findings that lower housing density and permanent breeding cage, together or separately, may enhance reproduction particularly in multiparous blue fox vixens.     

The effect of sex and shoal size on shoaling behaviour in Danio rerio

Male and female zebra fish Danio rerio were given choices of shoals that differed in sex and size. Male zebra fish preferred to associate with female shoals over male shoals, but had no preference when given a choice between a mixed‐sex shoal and either a male or female shoal. Female zebra fish showed no significant preference when given a choice between male and females shoals, nor between mixed‐sex shoals and either male or female shoals. When given choices between shoals of differing size, females preferred to associate with the larger shoal, whether or not they were composed of males or females. Males, however, had no preference for larger shoals over smaller shoals, whether or not they were composed of males or females. These results showed that male zebra fish were capable of distinguishing between males and females solely on the basis of visual cues. Furthermore, these results demonstrated a significant difference between the shoaling choices of male and female zebra fish, which may indicate a difference in the function of shoaling for the two sexes.     

Pen size and parity effects on maternal behaviour of Small-Tail Han sheep

The aim of this experiment was to study the effects of pen size and parity on maternal behaviour of twin-bearing Small-Tail Han ewes. A total of 24 ewes were allocated to a 2×2 design (six per pen), with parity (primiparous or multiparous) and pen size (large: 6.0×3.0 m; small: 6.0×1.5 m) as main effects at Linyi University, Shandong Province, China. Behaviour was observed from after parturition until weaning. All ewes were observed for 6 h every 5 days from 0700 to1000 h and from 1400 to 1700 h. Continuous focal animal sampling was used to quantify the duration of maternal behaviours: sucking, grooming and following as well as the frequency of udder accepting, udder refusing and low-pitched bleating. Oestradiol and cortisol concentrations in the faeces (collected in the morning every 5 days) were detected using EIA kits. All lambs were weighed 24 h after parturition and again at weaning at 35 days of age. The small pen size significantly reduced following (P<0.005), grooming (P<0.001) and suckling durations (P<0.05), as well as the frequency of udder refusals (P<0.001). However, there was a significant interaction with ewe parity, with decreased grooming and suckling in the small pen largely seen in the multiparous ewes (P<0.001). Independent of pen size, multiparous ewes accepted more sucking attempts by their lambs (P<0.05) and made more low-pitched bleats than primiparous ewes (P<0.001). Multiparous ewes had higher faecal oestradiol concentrations than primiparous ewes (P<0.001), and ewes in small pens had higher faecal cortisol levels compared with ewes in larger pens (P<0.001). As lambs increased in age, the duration of maternal grooming, following and suckling as well as frequency of udder acceptance and low-pitched bleating all declined, and the frequency of udder refusing increased (P<0.001 for all). Ewe parity, but not pen size, affected lamb weight gain during the period of observation (P<0.001). This is the first study to show that pen size, interacting with parity, can affect the expression of maternal behaviour in sheep during lactation. The study is also the first to report on the maternal behaviour of Chinese native sheep breeds (Small-Tail Han sheep), with implications for the production of sheep in China.     

Effect of housing conditions on activity and lying behaviour of horses

Housing conditions for horses impose various levels of confinement, which may compromise welfare. Lying behaviour and activity can be used as welfare indicators for domestic animals and rebound behaviour suggests a build-up of motivation resulting from deprivation. The objective of this study was to determine if activity and lying behaviour of horses are affected by housing conditions and to investigate the occurrence of rebound behaviour after release from confinement. Eight horses were subjected, in pairs, to each of four experimental treatments; paddock (P), fully stabled (FS), partly stabled (PS) and yard (Y). Each horse received 6 days acclimatisation prior to the 24 h recording period. Time spent in lying and activity were electronically recorded using a tilt switch and motion sensor connected to a data logger worn on the horse's left foreleg. Time spent active during the first 5 min of release from stable to paddock in the PS treatment (days 1 and 5) and at the same time of day in the P treatment was used as a measure of rebound behaviour. Effect of housing conditions on total time spent active was highly significant (FS = 123 s, PS = 158 s, Y = 377 s, P = 779 s, P < 0.001). Housing conditions did not significantly affect total time spent lying (P = 0.646). Horses were significantly more active, compared with baseline paddock behaviour, on release from stabling on both days 1 (P = 0.006) and 5 (P = 0.025) of PS treatment. These results suggest that activity patterns of horses, but not lying behaviour, are affected by the housing conditions tested and that rebound activity occurs in horses after a period of confinement.     

Effect of Sub-Polar Gyre, North Atlantic Oscillation and ambient temperature on size and abundance in the Icelandic Arctic fox

Animals are exposed to environmental factors that influence their life history and body size. Here we used the Arctic fox ( Vulpes lagopus ) as an indicator of the complex links between largescale environmental variables that influence both marine and tundra trophic dynamics to demonstrate how they affect the fox's body size and abundance. The Arctic fox inhabits throughout Iceland, where it preys mainly on birds. We studied the effects of the Sub-Polar Gyre (SPG), winter and summer North Atlantic Oscillation (NAO), mean annual winter and summer temperature, and geographic sector (eastern and western Iceland, which differ in their ecology) on variations in mandible size (6345 specimens) and body mass (2732 specimens) as well as abundance on the Arctic fox in Iceland. We found that (a) SPG index negatively affected male mandible length as well as body mass of both sexes. SPG was also negatively related to fox abundance. (b) Summer NAO had a negative effect on Arctic foxes, that is, cold summers were correlated with shorter mandibles and lower body mass. (c) Winter NAO had a significant negative effect (although weaker than that of summer NAO) on female mandible length, but not on body mass. (d) Summer temperature had a positive effect on female mandible length, but no effect on body mass. However, winter temperature had no effect on either the mandible or body mass. (e) Foxes in the eastern sector had shorter mandibles and were of lighter mass than those in the western sector. We suggest that climate conditions during the growth period of the young affected their final size both directly, by influencing energy metabolism for maintenance, but mainly through their effects on food availability. As far as we are aware, this is the first report that the SPG has an effect on vertebrates, let alone terrestrial ones.     

Effects of social environment on welfare status and sexual behaviour of female pigs. II. Effects of space allowance

This study examined the effects of housing groups of adult female pigs (6 pigs per group) with a space allowance of 1, 2 or 3 m² per pig on sexual behaviour and welface status, determined by plasma free-corticosteroid concentrations. A lower percentage of gilts was detected in oestrus and a lower percentage of gilts was mated when housed with a space allowance of 1 m² per gilt than with a space allowance of either 2 or 3 m² per gilt (oestrus detection rate of 79, 88 and 100%, respectively, and a mating rate of 77, 85 and 97%, respectively). There was a significant increase in plasma free-corticosteroid concentrations when gilts were housed with a space allowance of 1 m² per gilt. The elevated free corticosteroid levels of gilts in the 1 m² per gilt treatment suggests that a chronic stress response due to crowding may have been responsible for the apparent impairment in the sexual behaviour of these animals.     

Effect of access to outdoor grazing and stocking density on space and pasture use,behaviour, reactivity,and growth traits of weaned rabbits

In a context of evolving concern over housing conditions of farmed rabbits, we developed a housing system that allows access to an outdoor area. The aim was to study the health status, growth and behaviour of rabbits raised at two stocking densities with access to a paddock, or not. We distributed 299 weaned rabbits in four groups (YH: 100, NH: 99, YL: 50 and NL: 50) using a 2 × 2 factorial design including access (Y: yes) or not (N: not) to a 23 m² paddock and the indoor stocking density (H, high: 17 or L, low: 9 rabbits/m²). We measured the growth and health status of each animal weekly for 42 days (from 31 to 73 days of age) and performed reactivity tests to a new environment, a human and new object. We also assessed the rabbits’ behaviour at days 26 and 40 by doing a visual scan of each animal at regular time intervals. Our results showed that stocking density had no effect on mortality, but mortality tended to increase with outdoor access from 3.0% to 7.0% (P < 0.10). Although the stocking density had no effect on average daily gain, it was higher in rabbits in the N group than in the Y group (+3.6 g/day; P < 0.05). Rabbits entered the paddocks for the first time in less time at the beginning of the trial (50 s at day 3 vs 10 min at day 31; P < 0.001). The proportion of rabbits outside after 20 min of the new environment test was higher among rabbits in the L group than in the H group (+24% points at day 3 and +11% points at day 20; P < 0.001). Regardless of the stocking density, more rabbits in the N group touched the experimenter’s hand (16% vs 27%; P < 0.05) and the new object (34% vs 20%; P < 0.05) than rabbits in the Y group. Inactivity was more frequent in rabbits inside the pens than in the paddocks (70.0% vs 34.2% at days 26 and 40; P < 0.05). Locomotion was more frequent in the paddocks than in the indoor pens (20.0% vs 7.2% at days 26 and 40; P < 0.05). The stocking density did not affect the behavioural traits measured. In conclusion, providing rabbits access to a paddock could allow them to fulfil some natural behaviours but slightly reduced their growth.     

Experimental test of the influence of light availability on the evolution of eye size and behaviour in Daphnia

There exists extensive variation in eye size. Much work has provided a connection between light availability and differences in eye size across taxa. Experimental tests of the role of the light environment on the evolution of eye size are lacking. Here, we performed a selection experiment that examined the influence of light availability on shifts in eye size and the connection between eye size and phototactic (anti-predator) behaviour in Daphnia. We set-up replicate experimental populations of Daphnia, repeatedly evaluated phenotypic shifts in eye size during the ~50-day experiment, and performed a common garden experiment at the end of the experiment to test for evolutionary shifts in eye size and behaviour. Our phenotypic analyses showed that eye size rapidly diverged between the light treatments; relative eye size was consistently larger in the low versus high light treatments. Selection on eye size was also modified by variation in density as increases in Daphnia density favoured a larger eye. However, we did not observe differences in eye size between the light treatments following two generations of common garden rearing at the end of the experiment. We instead observed strong shifts in anti-predator behaviour. Daphnia from the low light treatment exhibited decreased phototactic responses to light. Our results show that decreased light relaxes selection on anti-predator behaviour. Such trends provide new insights into selection on eye size and behaviour.     

Effect of space allowance and floor type on performance,welfare and physiological measurements of finishing beef heifers

Accommodating cattle indoors during the winter is widely practiced throughout Europe. There is currently no legislation surrounding the space allowance and floor type that should be provided to cattle during this time, however, concerns have been raised regarding the type of housing systems currently in use. The objective of the study was to investigate the effect of space allowance and floor type on performance and welfare of finishing beef heifers. Continental crossbred heifers (n=240: mean initial live; weight, 504 (SD 35.8) kg) were blocked by breed, weight and age and randomly assigned to one of four treatments; (i) 3.0 m², (ii) 4.5 m² and (iii) 6.0 m² space allowance per animal on a fully slatted concrete floor and (iv) 6.0 m² space allowance per animal on a straw-bedded floor, for 105 days. Heifers were offered a total mixed ration ad libitum. Dry matter intake was recorded on a pen basis and refusals were weighed back twice weekly. Heifers were weighed, dirt scored and blood sampled every 3 weeks. Whole blood was analysed for complete cell counts and serum samples were assayed for metabolite concentrations. Behaviour was recorded continuously using IR cameras from days 70 to 87. Heifers’ hooves were inspected for lesions at the start of the study and again after slaughter. Post-slaughter, carcass weight, conformation and fat scores and hide weight were recorded. Heifers housed at 4.5 m² had a greater average daily live weight gain (ADG) than those on both of the other concrete slat treatments; however, space allowance had no effect on carcass weight. Heifers accommodated on straw had a greater ADG (0.15 kg) (P<0.05), hide weight (P<0.01) better feed conversion ratio (P<0.05) and had greater dirt scores (P<0.05) at slaughter than heifers accommodated on concrete slats at 6.0 m². The number of heifers lying at any one time was greater (P<0.001) on straw than on concrete slats. Space allowance and floor type had no effect on the number of hoof lesions gained or on any of the haematological or metabolic variables measured. It was concluded that increasing space allowance above 3.0 m²/animal on concrete slats was of no benefit to animal performance but it did improve animal cleanliness. Housing heifers on straw instead of concrete slats improved ADG and increased lying time; however carcass weight was not affected.     

Effect of local spatial plant distribution and conspecific density on bumble bee foraging behaviour

1. Size variations in pollinator populations may modify competitive interactions among foragers. Competition among pollinators has been shown to lead to one of two contrasting behaviours: either specialisation to the most profitable plant species or generalisation to several species. When foraging, pollinators are also confronted with heterogeneity in the spatial distribution of plant resources. Because variations in both the forager density and plant spatial distribution can affect pollinator behaviour, focus was on the interactive effect of these two factors. 2. Bumble bee (Bombus terrestris L.) individuals were trained on a focal species (Lotus corniculatus L.) and experimentally tested whether variations in the forager density (two or six bumble bees foraging together), plant community spatial distribution (two plant species: L. corniculatus and Medicago sativa, which were either patchily or randomly distributed), and their interaction modified bumble bee foraging behaviour. 3. It was shown that when confronted with a high forager density, bumble bees focused their visits towards the most familiar species, especially when foraging under a random plant distribution. These modifications affected the fruiting of the focal plant species, with a significantly lower reproductive success under low density/patchy conditions. 4. This study demonstrates that the foraging decisions of bumble bees are influenced by variations in both the conspecific density and plant spatial distribution. Given the increasing impact of human activities on plant‐pollinator communities, this raises the question of the potential implications of these results for plant communities in natural conditions when confronted with variations in the pollinator density and spatial distribution of plants.     

Effect of prey density on behaviour and development of the predatory mosquito,Toxorhynchites towadensis

The effect of prey density on feeding behaviour, killing behaviour, and development of the predatory mosquito,Toxorhynchites towadensis, was investigated in the laboratory. The number of prey consumed per larva increased toward an upper asymptote as prey density increased. Prey consumption curves during fourth instar were concave at low prey densities but convex at high prey densities. This phenomenon was not observed during other instars. Killing without consuming any part of prey occurred at prey densities of 20 per container and over. The number of prey killed but not consumed increased linearly with the number of unconsumed prey in the container. Prey acquisition behaviour was not affected by prey densities during the prepupal period. Developmental time from first instar to adult emergence decreased with increasing prey densities, but remained constant at densities of 10 per container and over. Adult size increased with increasing prey densities but there was no effect at prey densities of 20 and over.     

Notes on New Zealand mammals 10. Effect of observer position on group size and level of aggression of mating brown hares

Abstract

The sex pheromones of two endemic New Zealand tortricid species were investigated. Females of the first species, Cnephasia jactatana, a pest of kiwifruit, were found to produce (Z)-11-tetradecenyl acetate (Z11-14:OAc) in their sex pheromone gland. When tested in the field, this compound on its own elicited significant catches of male C. jactatana. However, the addition of even very small amounts (0.3%) of the geometric isomer, (E)-11-tetradecenyl acetate (E11-14:OAc), to Z 11-14:OAc virtually suppressed trap catches. The sex pheromone of the second species, Merophyas leucaniana, was found to consist of a mixture of Z11-14:OAc, E11-14:OAc, tetradecyl acetate, and (Z)-11-tetradecenol. This species is morphologically very similar to the congeneric species, M. divulsana, the Australian lucerne leafroller. The sex pheromone of M. leucaniana is also very similar to that of the so-called “Z-type” of M. divulsana, which is now found in New Zealand. The pheromone components of C. jactatana and M. leucaniana are discussed in relation to those found in other tortricids.     

Effect of rearing density on pecking behaviour and plumage condition of laying hens in two types of aviary

The objective of this experiment was to investigate the effect of rearing density on pecking behaviour and plumage during rearing and throughout the laying period in aviaries. Chicks were reared on sand at high (H; 13 m⁻²) or low (L; 6.5 m⁻²) density, in four rearing pens of 390 chicks and eight pens of 195 chicks, respectively, each pen measuring 30 m². Proportions of chicks per pen performing various types of pecking behaviour were recorded by scan sampling during 16 observation bouts in each rearing pen at 6 weeks of age and during 24 observation bouts at 12 weeks. Individual body weights and plumage condition were recorded. Later, these pullets were housed at 17 hens m⁻² in Tiered Wire Floor (TWF; 3 H and 3 L pens of 275 hens) and Laco-Volétage (2 H and 2 L pens of 275 hens) aviaries. At 35 weeks, two samples of eight hens from each aviary pen were observed for pecking behaviour in a test pen. Throughout the laying period, additional records were collected on pecking behaviour, body weight, plumage condition, egg production, and mortality. The L birds had better plumage condition at 6 weeks of age and throughout the laying period. These birds also ground pecked more frequently than H birds during rearing and the laying period. At 12 weeks, L birds feather pecked less than H birds, but no relationship was found between rearing density and feather-pecking behaviour during the laying period. Although TWF hens feather pecked more frequently than Volétage hens, there was no interaction between rearing density and type of aviary for the various pecking behaviours.     

Effect of paired encounters on plasma androgens and behaviour in males and females of the spiny damselfish Acanthochromis polyacanthus

Sexually mature male and female spiny damselfish, Acanthochromis polyacanthus (Pomacentridae) were introduced to resident fish of both sexes in paired encounter trials and the effect on activity, agonistic behaviour and plasma levels of testosterone (T) and 11-ketotestosterone (11-KT) in males, and T and 17β-estradiol (E₂) in females, and cortisol in both sexes was determined. Introduced males showed suppressed levels of T in the presence of both resident males and females, whereas resident males showed elevated T in response to introduced males but not females. Plasma 11-KT levels were unchanged in either resident or introduced males. Resident males showed increased activity in the presence of males but not females. Resident females showed an increase in activity when paired with introduced females and greater aggressive behaviour towards females than males. There were no differences in plasma hormone levels in either resident or introduced female fish. Plasma cortisol levels were low in all fish and stress effects did not appear to account for differences in T levels in males. The results of the present study show that elevations in plasma T levels in resident male spiny damselfish are associated only with male presence but that suppression of T in introduced fish occurs irrespective of the sex of the resident. In contrast resident females, which show stronger evidence of aggressive behaviour do not show changes in plasma androgen levels. This suggests that aggressive behaviour in male and female fishes may be mediated by different endocrine pathways.     

Effect of water velocity and temperature on energy use,behaviour and mortality of pallid sturgeon Scaphirhynchus albus larvae

Natural reproduction of pallid sturgeon Scaphirhynchus albus has been limited for decades and a recruitment bottleneck is hypothesized to occur during the larval stage of development. In this study, we evaluated the effects of water velocity and temperature on the swimming activity, energy use, settling behaviour and mortality of endogenously feeding larvae. The swimming activity of drifting sturgeon larvae (i.e., fish exhibiting negative rheotaxis) increased at low water velocity. In subsequent experiments, we observed greater energy depletion and resultant mortality of larvae in no-flow environments (0 cm s⁻¹) compared to tanks with water velocity ranging from 3.5 to 8.3 cm s⁻¹. The growth rate of drifting larvae was positively related to water temperature (18.7–23.3°C), but reduced growth rate at low water temperature (18.7°C) resulted in protracted development that extended average drift duration by ~4 days compared to larvae reared at 23.3°C. This study provides evidence that cooler summer water temperatures, characteristic of present-day conditions in the upper Missouri River, can reduce larval development and extend both the drift duration and distance requirements of S. albus. Moreover, if dispersed into low velocity environments, such as in reservoir headwaters, larvae may experience increased mortality owing to a mismatch between early life stage drift requirements and habitat conditions in the river. Manipulation of water releases to increase seasonal water temperature below dams may aid survival of S. albus larvae by shortening the time and distance spent drifting.