Furnished cages for laying hens: study of the effects of group size and litter provision on laying location, zootechnical performance and egg quality

The furnished cage is a new housing system for layers. A current trend in furnished cage design is to increase group size and replace the litter box with a mat provided with litter. An experiment was set up to determine the effects of group size and litter provision on laying performance and egg quality of beak-trimmed ISA Brown hens housed in large furnished cages with more than 12 hens. Six treatments, each of 18 furnished cages (768 cm(2)/hen including nest and litter area) were compared in a 3 × 2 experimental trial: three group sizes (S20 (20 hens per cage), S40 (40) and S60 (60)), with or without feed as litter distributed on the mat of the litter area. The provision of facilities per hen was equal in all treatments. Mortality, laying rate, mean egg weight, feed intake and feed conversion ratio were unaffected by group size over the 53-week laying period, and performance exceeded the ISA production standards. The overall percentage of eggs laid in the nest exceeded 95% except that it was slightly lower in group S20 (92.0% ± 6.4% v. S40: 96.0% ± 3.3% and S60: 96.2% ± 2.7%) leading to a higher proportion of dirty eggs (S20: 1.6% ± 2.2%, S40: 1.4% ± 1.5%, S60: 1.0% ± 1.0%). At 66 to 70 weeks, eggs laid outside the nest had a slightly higher count of mesophilic bacteria on the eggshell (5.0 log CFU/egg ± 0.4) than those laid in the nest (4.8 log CFU/egg ± 0.5) but no difference in contamination was observed between group sizes. Litter provision had no effect on mortality, egg weight or egg quality traits except for a higher proportion of broken eggs in cages with litter (5.3% ± 6.2% v. 4.6% ± 5.7%). Providing hens with feed for litter was associated with a higher laying rate (97.3% ± 3.2% v. 94.8% ± 4.4% at 23 weeks) and an apparent improvement in feed efficiency at the beginning of the laying period (feed conversion ratio based on feed consumption at the trough: 2.18 ± 0.06 with litter v. 2.28 ± 0.09 without litter at 25 weeks). The results of this study showed that a high level of productivity and good egg quality could be obtained in large furnished cages. Further research is needed to assess the impact on hens' welfare and performance of using more economically competitive substrates than feed for litter.     

Motivation to dust-bathe of laying hens housed in cages and in aviaries

New housing systems for commercial egg production, furnished cages and non-cage systems, should improve the welfare of laying hens. In particular, thanks to the presence of a litter area, these new housing systems are thought to satisfy the dust-bathing motivation of hens more than in conventional cages, in which no litter area is present. However, although apparently obvious, there is no concrete evidence that non-cage systems, particularly aviaries, satisfy hens' motivation to dust-bathe and thus improve hens' welfare in terms of dust-bathing behaviour. The aim of this study was to compare hens' dust-bathing motivation when housed for a long time under similar conditions to commercial conditions in laying aviaries (with litter) and in conventional cages (without litter). Three treatments were compared: hens reared in floor pens then housed in conventional cages, hens reared in furnished floor pens then housed in a laying aviary, and hens reared in rearing aviaries then housed in a laying aviary. All three treatments provided access to litter during the rearing period. After transfer to the laying systems, access to litter was maintained for the aviary hens but stopped for the cage hens. Twelve groups of four hens per treatment were tested 36 to 43 weeks after transfer. The hens were placed in sawdust-filled testing arenas, and latency to dust-bathe, duration and number of dust baths, and number of hens dust-bathing were recorded. Latency to dust-bathe was shorter, dust baths were longer and more numerous and more hens dust-bathed among cage hens than among aviary hens. Our results indicate that hens' motivation to dust-bathe was more satisfied in laying aviaries than in conventional cages. Thus, laying aviaries improve hens' welfare in term of dust-bathing behaviour compared with conventional cages.     

Complex housing environment for farmed blue foxes (Vulpes lagopus): use of various resources

The present study was designed to measure the use of various, simultaneously available resources in a complex housing environment in juvenile blue foxes. Twelve blue fox sibling (male–female) pairs were housed in two-section experimental cages from the age of 8 weeks until the age of 7 months (from June to December). Each experimental cage was furnished with two platforms, a nest box, a sand box and a wooden block. This housing set-up provided the foxes with social contact, and an opportunity for oral manipulation, scratching and nesting, as well as the choice of staying on a solid floor material or on an elevated location. The foxes’ behaviour was recorded at three time points during autumn (September, November and December). The foxes used all available resources. The most utilised resource was the nest box, possibly because it could be utilised in several ways (as a shelter, an elevated location, an object for scratching and for oral manipulation). The foxes also stayed more in the cage section containing the nest box than in the cage section containing a sand box. The foxes rested much on the cage floor, but they also used the interior of the nest box and elevated locations for resting. Social contact often occurred during resting. Thus, the nest box and elevated location, in conjunction with social contact seem to be valuable while resting. While active, the foxes utilised the cage floor and roof of the nest box instead of the platforms. Scratching, digging and an interaction with the wooden block were seldom observed. Activity occurred mainly on the ‘empty’ cage area. In conclusion, all studied resources provided blue foxes with a distinct value, as they all were used in the complex housing environment. The nest box is used most and for most variable behaviours.     

Does Rearing Laying Hens in Aviaries Adversely Affect Long-Term Welfare following Transfer to Furnished Cages?

This study tests the hypothesis that hens that are reared in aviaries but produce in furnished cages experience poorer welfare in production than hens reared in caged systems. This hypothesis is based on the suggestion that the spatial restriction associated with the transfer from aviaries to cages results in frustration or stress for the aviary reared birds. To assess the difference in welfare between aviary and cage reared hens in production, non-beak trimmed white leghorn birds from both rearing backgrounds were filmed at a commercial farm that used furnished cage housing. The videos were taken at 19 and 21 weeks of age, following the birds'' transition to the production environment at 16 weeks. Videos were analysed in terms of the performance of aversion-related behaviour in undisturbed birds, comfort behaviour in undisturbed birds, and alert behaviour directed to a novel object in the home cage. A decrease in the performance of the former behaviour and increase in the performance of the latter two behaviours indicates improved welfare. The results showed that aviary reared birds performed more alert behaviour near to the object than did cage reared birds at 19 but not at 21 weeks of age (P = 0.03). Blood glucose concentrations did not differ between the treatments (P>0.10). There was a significant difference in mortality between treatments (P = 0.000), with more death in aviary reared birds (5.52%) compared to cage birds (2.48%). The higher mortality of aviary-reared birds indicates a negative effect of aviary rearing on bird welfare, whereas the higher duration of alert behavior suggests a positive effect of aviary rearing.     

The effect of preweaning and postweaning housing on the behaviour of the laboratory mouse (Mus musculus)

Standard housing for laboratory mice severely restricts natural behaviour and the control that the animal has over its environment. Providing the cage with objects is a method that has been used to both increase environmental complexity, promote the performance of natural behaviour and provide greater controllability for the animal. This method of furnishing cages has mostly been studied in adult animals, and little is known about the influence that the preweaning environment has on the behaviour of mice as adults. This study aimed to investigate the effects on mice behaviour of preweaning and postweaning housing environment. In this experiment, 64 pairs of animals of the strain C57BL/6J were used. Half of the animals were born and reared until weaning in standard cages and the other half in cages twice the size of the standard and furnished with nesting material, a cardboard tube, a PVC nest box and a wooden chewblock. After weaning, half the animals in each group were changed to the other type of cage, whereas the other half remained in the same environment; in both cases they were kept in single-sex pairs of littermates. Behaviour during the dark, active period was studied through video recordings. We found no main effects of preweaning environment on behaviour; however, mice moved from furnished to standard cages at weaning showed a decrease in inactive behaviour at four weeks of age. Mice housed after weaning in standard cages spent less time inactive, and more time engaging in activities like feeding and drinking, self-grooming and allogrooming. A sex difference was also found, in that females showed a greater performance of exploratory behaviour as well as a greater prevalence of stereotypies. The use of different objects and locations within the furnished cage was also analysed at both ages. Results show that at eight weeks of age mice spent more time at the top of the cage, and that the use of the nest box (although not for resting) increased between four and eight weeks. Mice were found to use the nest box as a nesting site/sleeping place only at age four weeks, whereas they always used the nesting material for sleeping.     

Testing resource value in group-housed animals: an investigation of cage height preference in laying hens

To avoid unpredictable social effects, animals' behavioural priorities are almost always tested using individuals housed singly, yet many species kept commercially are social animals housed in groups. Our aim was to develop a method of investigating environmental preference in group-housed laying hens, Gallus gallus domesticus, that maximised the external validity of our findings. In a simple test of preference, eight groups of ten hens were given free choice between furnished cages with minimum heights of 38 cm (low) and 45 cm (high). A preference for one cage height over the other would be evident as a shift from a binomial distribution of flock sizes in the two cages. No height preference was found as hens distributed evenly between the two cages more frequently than was expected. This suggests at high stocking densities maximising average inter-individual distance could be a priority over increased cage height. In a second experiment, to investigate the value that hens placed on a change in cage height; a 'cost' in the form of a narrow gap was imposed on movement from a low or high start cage to a high or low target cage, respectively. Cage height did not influence the latency of the first three hens to enter the target cage. However, latencies for subsequent hens were shorter and more hens worked to access a high target cage than a low target cage. We suggest that titrating animals' willingness to tolerate higher stocking densities against access to a resource could be an effective way to compare responses of group-housed animals to resources that are expected to satisfy the same motivational state.     

Nest preference of laying hens (Gallus gallus domesticus) and their motivation to exert themselves to gain nest access

In connection with the development of a test method for the attractiveness and appropriateness of nests for laying hens, we carried out an investigation by using a preference test and motivation measuring with the help of push doors. Hens were offered two different nest sites either consisting of a tray filled with wood shavings (litter tray) or a wooden nest box plus wood shavings (nest box). Hens were individually housed in pens (2.0 m × 2.0 m) and had free access to the nest sites until they laid their 15th egg. From that day the hens had to overcome a push door to reach the nest sites. Resistance for entrance was also increased stepwise at the door leading to the hens’ nest. The experiment ended when a hen stopped to lay in her usual nest site for four consecutive days (postexperimental period). The behaviour during the last hour before oviposition was video taped at a level of resistance of 3.5, 6.0, 7.5 and 10.0 N.The hens were categorized into nest and litter layers depending on nest choice. All but one hen pushed maximum resistances between 11.5 and 18.0 N with no differences between nest and litter layers. Behaviour did not significantly change with increasing levels of resistance, but there were significant differences between nest and litter layers. Nest layers spent more time nesting than litter layers while the latter showed a strong tendency to more exploring behaviour. For litter layers, more entries through the push door leading to their nest site and more unsuccessful pushes were detected than for nest layers. According to our results, two types of layers could be distinguished whereas the two were equally motivated to access their nest site.     

The Influence of the Location of a Nest Box in an Individually Ventilated Cage on the Preference of Mice to Use It

The improvement of housing conditions for mice by using environmental enrichment materials is of high concern for the scientific community. Plastic, autoclavable nest boxes are commercially available and ready to use for specific cases such as in individually ventilated cages, metabolic cages, or during toxicological studies. The aim of this study was to see if the location of the nest box within the cage could influence the mice to prefer and use it. Located on the cage floor or hung from the cage lid, a nest box (MPLEX, Otto Environmental, Milwaukee, Wisconsin), enriched the cages. The study concluded that the location of the nest boxes in the individually ventilated cage plays a significant role in the mice preferring to use it or to avoid it. It is also important to use environmental enrichment items that provide animals with the possibility of expressing their preferences and manipulating them in a way to cope better with their environmental conditions.     

The influence of the location of a nest box in an individually ventilated cage on the preference of mice to use it

The improvement of housing conditions for mice by using environmental enrichment materials is of high concern for the scientific community. Plastic, autoclavable nest boxes are commercially available and ready to use for specific cases such as in individually ventilated cages, metabolic cages, or during toxicological studies. The aim of this study was to see if the location of the nest box within the cage could influence the mice to prefer and use it. Located on the cage floor or hung from the cage lid, a nest box (MPLEX, Otto Environmental, Milwaukee, Wisconsin), enriched the cages. The study concluded that the location of the nest boxes in the individually ventilated cage plays a significant role in the mice preferring to use it or to avoid it. It is also important to use environmental enrichment items that provide animals with the possibility of expressing their preferences and manipulating them in a way to cope better with their environmental conditions.     

Effects of housing conditions during the rearing and laying period on adrenal reactivity, immune response and heterophil to lymphocyte (H/L) ratios in laying hens

This study was conducted to evaluate the effect of early rearing conditions on physiological, haematological and immunological responses relevant to adaptation and long-term stress in white Leghorn hens with intact beaks housed in furnished cages (FC) or conventional cages (CC) during the laying period. Pullets were cage reared (CR) or litter floor reared (FR). From 16 to 76 weeks of age, hens were housed in FC (eight hens per cage) or in CC (three hens per cage). As measures of long-term stress at the end of the laying period, adrenal reactivity was quantified by assessing corticosterone responses to adrenocorticotropin challenge, and immune response was assessed by measuring antibody responses after immunization with sheep red blood cells (SRBC) and keyhole limpet haemocyanin (KLH). Heterophil to lymphocyte (H/L) ratio was employed as an indicator of stress. Rearing conditions significantly affected anti-SRBC titres (P < 0.0001) and tended to affect H/L ratios (P = 0.07), with the highest values found in FR hens. Layer housing affected H/L ratio (P < 0.01); the highest ratio was found in FR birds housed in FC during the laying period. This study shows that early rearing environment affects immunological indicators that are widely used to assess stress in laying hens. However, while results on H/L ratio indicated that FR birds experienced more stress particularly when they were housed in FC during the laying period, the immune responses to SRBC in FR hens was improved, indicating the opposite. This contradiction suggests that the effects on immune response may have been associated with pathogenic load due to environmental complexity in FR and FC hens rather than stress due to rearing system or housing system per se.     

Behaviour of laboratory mice in different housing conditions when allowed to self-administer an anxiolytic

Standard cages prevent mice from performing several natural behaviours for which they are motivated. As a consequence, abnormal behaviours sometimes develop and mice often spend long periods inactive. To improve welfare, cages are sometimes furnished with items such as nesting material, shelters and running wheels. We have previously reported that when allowed to self-administer an anxiolytic, mice in furnished cages consume less anxiolytic than mice in standard cages. This paper presents the results of behaviour studies of the mice in the same experiment. Female C57BL/6J mice (3 per cage) were housed in Standard (n = 10), Unpredictable (n = 10) or Furnished (n = 6) cages. Unpredictable cages were identical to Standard cages, but were exposed to unpredictable events two to three times a week. Furnished cages were double the size of Standard cages and contained nesting material, nest box, tubes, chew blocks and a running wheel. During three consecutive periods, mice had access to only water (control), water or an anxiolytic solution on a daily alternating schedule (forced consumption), and finally, both water and anxiolytic (self-administration). Behaviour was analysed from video recordings taken during the dark phase. The housing type affected behaviour both under the control and the self-administration conditions. Overall, mice in Furnished cages spent less time resting and performing bar-related behaviours and more time on exploratory/locomotory behaviours. Mice in Furnished cages also performed less bar-circling stereotypies than mice in Standard cages. The Unpredictable treatment did not significantly affect behaviour compared to mice in the Standard conditions. There was an overall effect of anxiolytic availability on rest-related behaviours and on exploration-locomotion behaviours, in that mice rested more and spent less time on exploration and locomotion when they were able to self-administer the anxiolytic.     

A machine vision system to detect and count laying hens in battery cages

Manually counting hens in battery cages on large commercial poultry farms is a challenging task: time-consuming and often inaccurate. Therefore, the aim of this study was to develop a machine vision system that automatically counts the number of hens in battery cages. Automatically counting hens can help a regulatory agency or inspecting officer to estimate the number of living birds in a cage and, thus animal density, to ensure that they conform to government regulations or quality certification requirements. The test hen house was 87 m long, containing 37 battery cages stacked in 6-story high rows on both sides of the structure. Each cage housed 18 to 30 hens, for a total of approximately 11 000 laying hens. A feeder moves along the cages. A camera was installed on an arm connected to the feeder, which was specifically developed for this purpose. A wide-angle lens was used in order to frame an entire cage in the field of view. Detection and tracking algorithms were designed to detect hens in cages; the recorded videos were first processed using a convolutional neural network (CNN) object detection algorithm called Faster R-CNN, with an input of multi-angular view shifted images. After the initial detection, the hens’ relative location along the feeder was tracked and saved using a tracking algorithm. Information was added with every additional frame, as the camera arm moved along the cages. The algorithm count was compared with that made by a human observer (the ‘gold standard’). A validation dataset of about 2000 images achieved 89.6% accuracy at cage level, with a mean absolute error of 2.5 hens per cage. These results indicate that the model developed in this study is practicable for obtaining fairly good estimates of the number of laying hens in battery cages.     

Pampas deer (Ozotoceros bezoarticus) male–female agonistic behavior toward high and low social ranked females

The pampas deer is an endangered species from the southern cone of South America. Although it is breed in confined groups, there is very scarce information on how their social relationships and aggressiveness are regulated in these groups. As we hypothesized that pampas deer males display different behaviors toward high or low social ranked females, we compared the number and pattern of agonistic behaviors used by pampas deer males to displace high- and low-ranked females. We performed focal observations recording all female–female agonistic interactions resulting in the displacement of an animal in six breeding groups (total?=?6 males and 31 females), and calculated the success index for each hind. Then, we recorded all male–female agonistic interactions while animals received food, and compared the total number and the type of interactions used by males to displace high- and low-ranked individuals. Males displaced more frequently high-ranked than low-ranked females (P?=?0.006), mainly by their presence (P?=?0.0004); males tended to displace low-ranked females more frequently by kicking (P?=?0.051). We designed a complementary study to determine if the male–female physical distances may explain that difference. We recorded male–female distances every 5 min for 30 min during 10 days while animals ate ration, and calculated an association index (AI) between each female with the male. Low-ranked females tended to have greater AI accumulated at 5 and 10-min scans (P?=?0.071 and 0.077, respectively) than high-ranked females. The changes in the AI may indicate that high-ranked females were displaced during the period with more interactions. We concluded that (1) pampas deer males displayed more agonistic interactions toward high-ranked than low-ranked females; (2) this difference was mainly due to a greater number of displacements of females by mere presence; (3) high-ranked females moved far from males than low-ranked females, reflecting different relationships between them.     

The Effect of Cooled Perches on Immunological Parameters of Caged White Leghorn Hens during the Hot Summer Months

The objective of this study was to determine if thermally cooled perches improve hen immunity during hot summer. White Leghorn pullets at 16 week of age were randomly assigned to 18 cages of 3 banks at 9 hens per cage. Each bank was assigned to 1 of the 3 treatments up to 32 week of age: 1) thermally cooled perches, 2) perches with ambient air, and 3) cages without perches. Hens were exposed to natural ambient temperatures from June through September 2013 in Indiana with a 4 h acute heat episode at 27.6 week of age. The packed cell volume, heterophil to lymphocyte (H/L) ratio, plasma concentrations of total IgG, and cytokines of interleukin-1β and interleukin-6, plus lipopolysaccharide-induced tumor necrosis factor-α factor were measured at both 27.6 and 32 week of age. The mRNA expressions of these cytokines, toll-like receptor-4, and inducible nitric oxide synthase were also examined in the spleen of 32 week-old hens. Except for H/L ratio, thermally cooled perches did not significantly improve currently measured immunological indicators. These results indicated that the ambient temperature of 2013 summer in Indiana (24°C, 17.1 to 33.1°C) was not high enough and the 4 h heat episode at 33.3°C (32 to 34.6°C) was insufficient in length to evoke severe heat stress in hens. However, cooled perch hens had a lower H/L ratio than both air perch hens and control hens at 27.6 week of age and it was still lower compared to control hens (P < 0.05, respectively) at 32 week of age. The lowered H/L ratio of cooled perch hens may suggest that they were able to cope with acute heat stress more effectively than control hens. Further studies are needed to evaluate the effectiveness of thermally cooled perches on hen health under higher ambient temperatures.     

Evaluation of the local population of Eretmocerus mundus (Hymenoptera: Aphelinidae) for biological control of Bemisia tabaci biotype B (Hemiptera: Aleyrodidae) in greenhouse peppers in Argentina

Bemisia tabaci biotype B is a key pest in pepper crops in Argentina. The parasitoid Eretmocerus mundus is frequently found parasitizing this whitefly in greenhouses without pesticide applications. The present studies were carried out with the objective of evaluating control obtained with different rate and number of parasitoid releases under experimental conditions. Release rate: cages with pepper pots were positioned in an experimental greenhouse and randomly assigned to the release rate treatments (0, 1 and 3 pairs of E. mundus/plant/week with a total of three introductions). Number of releases: similar cages were assigned to the number of parasitoid introduction treatments (0, 1, 2 and 3) with the best release rate obtained in the previous trial. In both assays whitefly (adults and nymphs) and parasitoid (parasitized nymphs) population sizes in each cage were monitored weekly for a period of 10 weeks. Results suggested that the introduction of 2 E. mundus/plant/week was enough to suppress host population compared to control treatment (peaks of 7.75 adults and 58.75 nymphs/cage and 643.75 adults and 1598 nymphs/cage, respectively) (p < 0.05), with 85% of parasitism. E. mundus had to be introduced three times to achieve the best pest control (peaks of 1.17 adults and 20.33 nymphs/cage vs. 55.67 adults and 75 nymphs/cage in control treatment) with 84% of parasitism (p < 0.05). These results were then validated in a pepper crop under experimental greenhouse conditions. Whitefly population was lower in those greenhouses where E. mundus was released compared to control greenhouses (0.15 adults and 0.71 nymphs/4 leaves and 0.73 adults and 1.64 nymphs/4 leaves, respectively), with a peak of 54% of parasitism (p < 0.05). We concluded that good suppression of B. tabaci could be achieved using E. mundus under spring conditions in Argentina.     

Timing,frequency, and duration of incubation recesses in dabbling ducks

Nest attendance is an important determinant of avian reproductive success, and identifying factors that influence the frequency and duration of incubation recesses furthers our understanding of how incubating birds balance their needs with those of their offspring. We characterized the frequency and timing (start time, end time, and duration) of incubation recesses for mallard (Anas platyrhynchos) and gadwall (Mareca strepera) hens breeding in Suisun Marsh, California, USA, and examined the influences of day of year, ambient temperature at the nest, incubation day, and clutch size on recess frequency and timing using linear mixed models. Mallard, on average, took more recesses per day (1.69 ± 0.80, mean ± standard deviation) than did gadwall (1.39 ± 0.69), and 45% of mallard nest‐days were characterized by two recesses, while only 27% of gadwall nest‐days were characterized by two recesses. Mallard morning recesses started at 06:14 ± 02:46 and lasted 106.11 ± 2.01 min, whereas mallard afternoon recesses started at 16:39 ± 02:11 and lasted 155.39 ± 1.99 min. Gadwall morning recesses started at 06:30 ± 02:46 and lasted 91.28 ± 2.32 min, and gadwall afternoon recesses started at 16:31 ± 01:57 and lasted 192.69 ± 1.89 min. Mallard and gadwall started recesses earlier in the day with increasing ambient temperature, but later in the day as the season progressed. Recess duration decreased as the season progressed and as clutch size increased, and increased with ambient temperature at the nest. The impending darkness of sunset appeared to be a strong cue for ending a recess and returning to the nest, because hens returned to their nests earlier than expected when recesses were expected to end after sunset. Within hens, the timing of incubation recesses was repeatable across incubation days and was most repeatable for mallard afternoon recesses and on days in which hens took only one recess. Hens were most likely to be away from nests between 04:00 and 07:00 and between 16:00 and 19:00; therefore, investigators should search for nests between 07:00 and 16:00. Our analyses identified important factors influencing incubation recess timing in dabbling ducks and have important implications for nest monitoring programs.     

Non-exclusive spatial preference in the laying hen

Two experiments were performed to elucidate aspects of the spatial preference of domestic hens kept in battery cages.In the first experiment, 12 hens were given a choice between four cages differing in size and shape. The measure of preference used was the amount of time spent in each cage under free-access conditions. The results show that the hens spent most time in the cage with the largest floor area, but that substantial amounts of time were spent in the remaining three cages. Eight possible explanations for this non-exclusive choice are proposed: variation among hens; change of preference with time; mis-identification; constraints on decision-making; pacing; sampling; monitoring; genuine preference. The first six hypotheses are discussed with respect to this experiment.The second experiment, using 6 hens under similar conditions, was designed to distinguish between the latter two hypotheses. The results suggest there may be a monitoring component to the hens' behaviour in this apparatus, characterised by cage visits of short duration. In addition, the hens may continue to visit small cages in order to perform particular behaviour patterns. Nest-building behaviour is mentioned as one possibility.     

Light-sampling behavior in photoentrainment of a rodent circadian rhythm

Summary Behavioral aspects of photoentrainment of circadian locomotor activity rhythms were recorded for a nocturnal den-dwelling rodent, the flying squirrel,Glaucomys volans. Methods included both telemetric monitoring and infrared observations of animals under constant dark (DD) or light-dark (LD) schedules in either standard wheel cages or in newly developed simulated den cages. By means of the den cages, several aspects of a circadian activity cycle could be simultaneously measured emphasizing the arousal from rest, the light-sampling behavior by which a squirrel assessed the environmental photoregimen, and the phase-shifting by which photoentrainment was achieved. Each animal in a den cage remained for 12 or more hours of its rest period almost exclusively in the darkened nest box, then at an abrupt arousal time moved to the light-sampling porthole. In darkness each animal initiated wheel activity immediately after arousal; light at arousal time, however, induced a return to the nest box for a nap and a delay phase-shift in onset of activity of approximately 40 min. On subsequent days, each animal appeared to be free-running ( _FR< 24 h) until onset again advanced into the light period. A squirrel usually viewed only a few minutes light per day, and on free-running days occasionally saw none of the 12-h light period. The significance of these data for theories of circadian photoentrainment is discussed.Abbreviations CT circadian time - PRC phase response curve - SCN suprachiasmatic nucleus     

A method for studying social and reproductive behaviour of subterranean rodents in captivity

A methodology for studying the social and reproductive behaviour of solitary subterranean rodents under laboratory conditions is proposed. A first account ofCtenomys talarum (Thomas, 1898) behaviour is also provided with the aim of evaluating the proposed methodology and to advance presently unknown information on its social behaviour and mating system. The device is a seminatural enclosure, departing from traditional test cages with respect to increased: (1) size, (2) structural complexity, (3) social complexity, and (4) resemblance to natural conditions. It consists of artificial burrows each comprising 3.5 m of tunnel, a resource cage and a nest box, resembling the structural complexity described forC. talarum burrows. Burrows are connected to a common space, which allows social interaction among various individuals. Animals were observed in the seminatural enclosure — 3 females and 2 males, in accordance with sex ratios found in natural populations — for a period of 6 months. We obtained data related to reproductive and social behaviour: marking, aggression, vocalization, courtship and copulation, pregnancy, pup development, and parental care. The proposed system enables the collection of behavioural data as yet unavailable due to the secretive habits and aggressiveness that characterize this group of rodents, coupled with the difficulties associated with simulating subterranean conditions.