Variability and periodicity of dustbathing behaviour in Japanese quail (Coturnix coturnix japonica)

The purpose of this study was to determine the amount of time invested in, and the distribution of, dustbathing behaviour over the course of a day. Amount of time spent dustbathing, preening, ingesting, and engaging in sexual/agonistic activities by individual quail was recorded for the light portion of selected photoperiods. Results indicate consistency in amounts of dustbathing exhibited by individual birds under the different photoperiods; amount of time spent dustbathing was intermediate with respect to the other behaviours recorded. A daily peak period of dustbathing was evident except under constant light conditions. These results are explained on the basis of selective pressures operating to maximize the efficiency of dustbathing.     

Mean surface temperature prediction models for broiler chickens—a study of sensible heat flow

Body surface temperature can be used to evaluate thermal equilibrium in animals. The bodies of broiler chickens, like those of all birds, are partially covered by feathers. Thus, the heat flow at the boundary layer between broilers’ bodies and the environment differs between feathered and featherless areas. The aim of this investigation was to use linear regression models incorporating environmental parameters and age to predict the surface temperatures of the feathered and featherless areas of broiler chickens. The trial was conducted in a climate chamber, and 576 broilers were distributed in two groups. In the first trial, 288 broilers were monitored after exposure to comfortable or stressful conditions during a 6-week rearing period. Another 288 broilers were measured under the same conditions to test the predictive power of the models. Sensible heat flow was calculated, and for the regions covered by feathers, sensible heat flow was predicted based on the estimated surface temperatures. The surface temperatures of the feathered and featherless areas can be predicted based on air, black globe or operative temperatures. According to the sensible heat flow model, the broilers’ ability to maintain thermal equilibrium by convection and radiation decreased during the rearing period. Sensible heat flow estimated based on estimated surface temperatures can be used to predict animal responses to comfortable and stressful conditions.     

Working for a dustbath: are hens increasing pleasure rather than reducing suffering?

Dustbathing is one of the major behavioural systems of domestic fowl that is constrained by commercial caging systems. Although research conducted over the last 20 years has revealed a great deal about causation of dustbathing, attempts at measuring the importance to hens of having access to dustbathing substrate have proven difficult. Various economic techniques, operant conditioning and learning trials have been used to determine whether hens have a 'need' for dustbathing substrate or 'think' about dustbathing in the absence of substrate. In this study, we measured hens' willingness to work to obtain substrate for dustbathing using a vertically swinging door to which weights could be added. Hens were trained to push through the door to enter a goal box containing peat moss. The hens were subjected to two series of trials to compare the maximum weight that they would push to open the door when living in a cage and deprived of dustbathing substrate, with the maximum weight that they would push when living in a pen furnished with litter and a dustbath (non-deprived). Of the 10 hens that opened the door for access to peat moss, six hens pushed more weight when deprived, three hens pushed more weight when non-deprived and one hen pushed an equal amount of weight. Overall, the hens tended to push more weight (860+/-95.6 vs. 682.5+/-83.3 g; P<0.10, one-tailed paired t-test) and tended to make more attempts to open the door (P<0.10) when they were deprived than when they were non-deprived. Significantly more trials resulted in dustbathing when hens were deprived (P<0.01) suggesting that following deprivation, the hens were, in fact, more motivated to dustbathe. The results of these trials indicate that although deprived hens may be more motivated to dustbathe, and that most hens may be willing to work to obtain a dusty substrate when they can see it, they are not necessarily willing to work harder when they are in a state of deprivation than when they have recently dustbathed. These results are very difficult to explain using a 'needs' model of motivation in which deprivation leads to a state of suffering. They are much more consistent with an 'opportunity' model of motivation in which performance of the behaviour, when the opportunity presents itself, leads to a state of pleasure.     

An evaluation of potential dustbathing substrates for commercial broiler chickens

Provision of an appropriate dustbathing substrate may allow broiler chickens to satisfy a natural motivation and give them an opportunity to exercise. The main aim of this study was to evaluate the extent to which different substrates promote dustbathing behaviour in broilers. The trial was replicated over three production cycles in one commercial broiler house, with ~22 000 Ross broilers housed per cycle. The birds were provided with access to five experimental substrates from day 10 of the 6-week production cycle. The substrates included the following: (1) peat (P), (2) oat hulls (OH), (3) straw pellets (SP), (4) clean wood shavings (WS), and (5) litter control (C). The substrates were provided in 15 steel rings (1.1 m in diameter, three rings per substrate) dispersed throughout the house. The level of occupancy of the rings, behaviours performed in each substrate, and the effect of ring position (central or edge of house) were assessed in weeks 3, 4, 5 and 6 using scan sampling from video footage. Where substrates successfully promoted dustbathing, the length and components of the bouts (including number of vertical wing shakes and ground pecks) were also assessed. Results showed that birds used P significantly more than the remaining substrates for dustbathing (P<0.001). Oat hulls were the second most preferred substrate for dustbathing, with significantly more birds dustbathing in the OH compared with SP, WS and C (P<0.001). The least sitting inactive was also seen in the P and OH rings compared with the SP, WS and C (P<0.001). The highest levels of foraging were recorded in the P, OH and WS compared with SP and the C. Position of the rings did not affect the types of behaviours performed in any substrate, although overall more birds were counted in the central compared with edge rings (P=0.001). More detailed information on dustbathing behaviour was only recorded in the P and OH treatments, and there were no differences in the length of dustbathing bout, or components of the bout between them (P>0.05). The use of OH is likely to be more environmentally sustainable than that of P, and our results suggest that this substrate is relatively successful in promoting dustbathing. However, a preference was still observed for P and further work should investigate whether other suitable substrates could better reflect its qualities.     

Some effects of temperature on the hour glass photoperiod timer in the aphid Megoura viciae

“Resonance” experiments conducted at 3 temperatures do not support the view that the Megoura photoperiod (scotophase) timer has an oscillatory component. The main effects of temperature, which are consistent with an hour glass model, have been examined by exposing the aphids to temperatures ranging from −3 to 30°C for the first 4 h of the scotophase, subsequently returning them in each cycle to 15°C for measurement of the critical night length. During the temperature treatments the insects were removed from the plant to avoid indirect effects resulting from changes in the rate of development (this procedure causes a slight shift in the critical night length from 9.5 to 9.0 h). The timer was found to be almost perfectly compensated between 6 and 20°C, but at lower temperatures it runs slow, only one quarter the normal elapsed time being measured at −3°C. At higher temperatures (25 and 30°C) considerable irregularities appear, eventually resulting in the elimination of the critical night length. The results suggest that the timer may sometimes be stopped.Light perception was assessed by cooling the aphids in light. Photoreception was impaired in some individuals at temperatures as high as +6°C and became negligible at −3°C. The illuminated phase was then accepted as a dark interval of equal duration. Yet at this temperature the timer was still operating, albeit slowly. Their differing temperature thresholds point to some degree of separation in these two functions.High-temperature (25°C) experiments with continously feeding aphids showed that although scotophase heating was more effective, there was a distinct response when high temperatures were synchronized with the photophase. This was attributed to the operation of a “photoperiod counter” mechanism.     

Dustbathing as a regulatory mechanism

Three mathematical models were developed to describe how some species of birds, such as bobwhite quail (Colinus virginianus) regulate the amount of oil on their plumage. The models assume that dustbathing plays a significant role in this regulatory process. They differed primarily in their assumptions about the relationship between oiling and dustbathing behavior. Several experiments were run to check on the implications of the models.     

Extrinsic light:dark cycles,rather than endogenous circadian cycles,affect the photoperiodic counter in the pitcher-plant mosquito, <Emphasis Type="Italic">Wyeomyia smithii</Emphasis>

A wide diversity of organisms use photoperiod (daylength) as an environmental cue to anticipate the changing seasons and to time various life-history events such as dormancy and migration. Photoperiodic time measurement consists of two main components, (1) the photoperiodic timer that discriminates between long and short days, and (2) the photoperiodic counter that accumulates and stores information from the timer and then induces the phenotypic output. Herein, we use extended night treatments to show that light is necessary to accumulate photoperiodic information across the geographic range of the mosquito, Wyeomyia smithii and that the photoperiodic counter counts extrinsic (external) light:dark cycles and not endogenous (internal) circadian cycles.     

The contribution of an hourglass timer to the evolution of photoperiodic response in the pitcher-plant mosquito, Wyeomyia smithii

Abstract Photoperiodism, the ability to assess the length of day or night, enables a diverse array of plants, birds, mammals, and arthropods to organize their development and reproduction in concert with the changing seasons in temperate climatic zones. For more than 60 years, the mechanism controlling photoperiodic response has been debated. Photoperiodism may be a simple interval timer, that is, an hourglasslike mechanism that literally measures the length of day or night or, alternatively, may be an overt expression of an underlying circadian oscillator. Herein, we test experimentally whether the rhythmic response in Wyeomyia smithii indicates a causal, necessary relationship between circadian rhythmicity and the evolutionary modification of photoperiodic response over the climatic gradient of North America, or may be explained by a simple interval timer. We show that a day-interval timer is sufficient to predict the photoperiodic response of W. smithii over this broad geographic range and conclude that rhythmic responses observed in classical circadian-based experiments alone cannot be used to infer a causal role for circadian rhythmicity in the evolution of photoperiodic time measurement. More importantly, we argue that the pursuit of circadian rhyth-micity as the central mechanism that measures the duration of night or day has distracted researchers from consideration of the interval-timing processes that may actually be the target of natural selection linking internal photoperiodic time measurement to the external seasonal environment.     

Influence of prior exposure to wood shavings on feather pecking, dustbathing and foraging in adult laying hens

It has been proposed that chicks acquire substrate preferences during an early 'sensitive' period. If a suitable substrate is absent during this period birds may develop alternative preferences for pecking at feathers. The aim of this study was to examine whether early substrate exposure has durable effects on the subsequent behaviour of adult hens. The effects of duration of substrate exposure, substrate change, age at exposure and time since exposure on adult bird behaviour were examined. From days 1 to 210, 144 laying strain birds were housed in pairs in pens with wire floors. The floors were replaced with solid floors covered in wood shavings at different ages and for different durations by allocation to 1 of 12 treatments. Adult birds that had never experienced shavings performed significantly more feather pecking than birds in any other treatment group. Thus, exposure to shavings, even for the minimum exposure duration of 10 days, was protective. However, current substrate was of great importance and adult birds housed on shavings performed significantly more ground pecking and less feather pecking than birds on wire, regardless of previous experience. From day 211 all hens were given shavings or straw, presented alternately for five 24h sessions over 10 consecutive days. Birds foraged on both substrates and their foraging behaviour was not influenced by previous experience. Dustbathing occurred primarily on shavings and was significantly influenced by the age at which birds had previously been exposed to shavings. Dustbathing on shavings was fairly constant throughout the 10-day test period in all groups, suggesting that relatively stable preferences had developed. A secondary 'sensitive period' for the formation of adult dustbathing substrate preference may have superseded the early 'imprinting' process. However, adult behaviour was generally flexible and strongly influenced by current substrate.     

Photoperiodic time measurement in the spider mite Tetranychus urticae: A novel concept

To explain photoperiodic induction of diapause in the spider mite Tetranychus urticae a new theoretical model was developed which took into account both the hourglass and rhythmic elements shown to be present in the photoperiodic reaction of these mites. It is emphasized that photoperiodic induction is the result of time measurement as well as the summation and integration of a number of successive photoperiodic cycles: the model, therefore, consists of separate ‘clock’ and ‘counter’ mechanisms. In current views involvement of the circadian system in photoperiodism is interpreted in terms of the hypothesis that the photoperiodic clock itself is based on one or more circadian oscillators. Here a different approach has been chosen as regards the role of the circadian system in photoperiodism: the possibility, previously put forward by other authors, that some aspect of the photoperiodic induction mechanism other than the clock is controlled by the circadian system was investigated by assuming a circadian influence on the photoperiodic counter mechanism. The derivation of this ‘hourglass timer oscillator counter’ model of photoperiodic induction in T. urticae is described and its operation demonstrated on the basis of a number of diel and nondiel photoperiods, with and without light interruptions.     

Accomplishment of time-interval activation of esterase A4 by simple removal of pin fraction

In the seasonal cycle of the silkworm Bombyx mori, an ATPase called esterase A4 (EA4) is thought to measure time interval as a diapause-duration timer. To address the mechanism by which EA4 measures the time, we present a simple EA4 screening method. By the method, EA4 activity can be assessed with a short incubation at 25°C without the need to purify the enzyme further. The method largely overcomes methodological problems that remain unanswered. Besides, the results obtained by the method establish that the time measurement is based on the moment when the time-holding factor(s) PIN (peptidyl-inhibitory needle) is removed. EA4 may originally be a complex with PIN, and external time cues such as winter cold may induce the dissociation of the complex, which in turn results in the timer activation of EA4.     

Universal Trap Timer Design to Examine Temporal Activity of Wildlife

Abstract: We designed a reliable and inexpensive universal trap timer that records the time from the moment a single-live-capture trap is triggered by an animal to when the observer checks the trap. Combined with trapping information, the diel activity pattern of a given species or demographic group can then be described or compared between imposed treatments. The universal trap timer is adaptable to operate reliably with most single-capture trap designs, requires no permanent modification of traps, and is easy to construct.     

Hematoxylin-Eosin Staining Adapted to Automatic Tissue Processing

A technique for hematoxylin-eosin staining in a Lipshaw tissue processor is described. Since the machine uses a 1 min minimum interval timer with a 20 min cycle and since the total time for the procedure is more than 20 min the timer must be permitted to run through two cycles and the staining program must comply with the inherent inflexibility of the timing mechanism. Such a program has been devised and is described. It provides for 6 min in Ehrlich's hematoxylin (followed by appropriate washes), 1 min in alcoholic eosin, and final passage through alcohols into xylene, after which the slides are ready for mounting. The quality and uniformity of the stained slides are as good as those obtained by hand staining.     

Time of consciousness, consciousness of time

Time shapes our behavior: we must estimate the duration of events in our environment in order to anticipate changes and time our activity in function of these changes. However, there is no sensory modality devoted to the perception of time, therefore the question is to know which mechanisms underlie the consciousness that time flows and allow us to estimate time precisely. This article proposes a brief overview of psychological, neuropsychological and brain imaging studies which rely on theoretical models postulating the existence of an internal timer. These studies examine the different components--time base, counter and memory--of this timer: particularly they are aimed at characterising the relationships between the evolution of these components with age or their pathological alterations and changes in temporal judgements. They also attempt to specify the neural bases of these components. From this brief overview comes the idea that, if an internal timer exits, it does not mark objective time but a multitude of subjective times.     

Behaviour, natural history, and annual cycle of the Henderson Island rail Porzana atra (Aves: Rallidae)

The little known endemic Henderson Island rail (or Henderson rail) Porzflna atra , inhabits forest on the coastal plain and upraised plateau of Henderson Island. Rails were studied for 15 months from January 1991 to March 1992. The population was estimated at c. 6200 individuals living in pairs or cooperative groups of 3–4 adults on territories averaging about 1 ha. Two or three eggs were laid in covered or open nests near the ground from mid-July to mid-February. Up to five consecutive nesting attempts were made in cases where eggs or young chicks were lost. Adults laid a second clutch when chicks were fully feathered at about one month of age. Both sexes incubated and helped rear the young. Older chicks sometimes helped feed younger siblings. Dispersal of juveniles from the natal territory took place in April. Adult birds underwent a rapid, simultaneous post-nuptial moult of the remiges in February-April; the post-juvenile moult involved body feathers only. Data on morphometries, breeding ecology, courtship behaviour and voice are compared with available information for the spotless crake P. tabuensis , the Henderson rail's closest relative and probable ancestor. These comparisons provide some information on how these two taxa have differentiated since rails arrived on Henderson Island some time in the last 380000 years.     

Biomechanics and physiology of gait selection in flying birds

Two wing-beat gaits, distinguished by the presence or absence of lift production during the upstroke, are currently used to describe avian flight. Vortex-visualization studies indicate that lift is produced only during the downstroke in the vortex-ring gait and that lift is produced continuously in the continuous-vortex gait. Tip-reversal and feathered upstrokes represent different forms of vortex-ring gait distinguished by wing kinematics. Useful aerodynamic forces may be produced during tip-reversal upstroke in slow flight and during a feathered upstroke in fast flight, but it is probable that downstroke forces are much greater in magnitude. Uncertainty about the function of these types of upstroke may be resolved when more data are available on wake structure in different flight speeds and modes. Inferring from wing kinematics and available data on wake structure, birds with long wings or wings of high aspect ratio use a vortex-ring gait with tip-reversal upstroke at slow speeds, a vortex-ring gait with a feathered upstroke at intermediate speeds, and a continuous-vortex gait at fast speeds. Birds with short wings or wings of low aspect ratio use a vortex-ring gait with a feathered upstroke at all speeds. Regardless of wing shape, species tend to use a vortex-ring gait for acceleration and a continuous-vortex gait for deceleration. Some correlations may exist between gait selection and the function of the muscular and respiratory system. However, overall variation in wing kinematics, muscle activity, and respiratory activity is continuous rather than categorical. To further our understanding of gait selection in flying birds, it is important to test whether upstroke function varies in a similar manner. Transitions between lifting and nonlifting upstrokes may be more subtle and gradual than implied by a binomial scheme of classification.     

Basic helix-loop-helix proteins and the timing of oligodendrocyte differentiation

An intracellular timer in oligodendrocyte precursor cells is thought to help control the timing of their differentiation. We show here that the expression of the Hes5 and Mash1 genes, which encode neural-specific bHLH proteins, decrease and increase, respectively, in these cells with a time course expected if the proteins are part of the timer. We show that enforced expression of Hes5 in purified precursor cells strongly inhibits the normal increase in the thyroid hormone receptor protein TR(&bgr;)1, which is thought to be part of the timing mechanism; it also strongly inhibits the differentiation induced by either mitogen withdrawal or thyroid hormone treatment. Enforced expression of Mash1, by contrast, somewhat accelerates the increase in TR(beta)1 protein. These findings suggest that Hes5 and Mash1 may be part of the cell-intrinsic timer in the precursor cells.     

Light-break experiments and photoperiodic time measurement in the spider mite Tetranychus urticae

To explain photoperiodic induction of diapause in the spider mite Tetranychus urticae (Acarina: Tetranychidae) a theoretical model was developed, consisting of two components, viz. a “clock” and a photoperiodic “counter” mechanism. The clock executes photoperiodic time measurement according to hourglass kinetics; the counter accumulates the photoperiodic information contained in a number of successive $\text{light}\text{dark}$ cycles by adding up the number of “long” and “short” nights experienced by the developmental stages of the mites sensitive to the photoperiod. The influence of the circadian system on photoperiodic induction is interpreted as an inhibitory effect exerted on the expression of the photoperiodic response; this effect is encountered only in certain photoperiodic regimes, where the circadian system and the photoperiod are out of “resonance” with each other. This “hourglass timer oscillator counter model”, devised to give a theoretical explanation of photoperiodic time measurement, the summation of photoperiodic information, and the influence of the circadian system on photoperiodic induction, proved to be consistent with experimental results obtained with T. urticae in both symmetrical and asymmetrical “skeleton” photoperiods, the latter based on diel as well as non-diel $\text{light}\text{dark}$ cycles.     

An intrinsic timer that controls cell-cycle withdrawal in cultured cardiac myocytes

Developing cardiac myocytes divide a limited number of times before they stop and terminally differentiate, but the mechanism that stops their division is unknown. To help study the stopping mechanism, we defined conditions under which embryonic rat cardiac myocytes cultured in serum-free medium proliferate and exit the cell cycle on a schedule that closely resembles that seen in vivo. The culture medium contains FGF-1 and FGF-2, which stimulate cell proliferation, and thyroid hormone, which seems to be necessary for stable cell-cycle exit. Time-lapse video recording shows that the cells within a clone tend to divide a similar number of times before they stop, whereas cells in different clones divide a variable number of times before they stop. Cells cultured at 33 degrees C divide more slowly but stop dividing at around the same time as cells cultured at 37 degrees C, having undergone fewer divisions. Together, these findings suggest that an intrinsic timer helps control when cardiac myocytes withdraw from the cell cycle and that the timer does not operate by simply counting cell divisions. We provide evidence that the cyclin-dependent kinase inhibitors p18 and p27 may be part of the timer and that thyroid hormone may help developing cardiac myocytes stably withdraw from the cell cycle.     

Quantitative Untersuchungen zu Wechselbeziehungen zwischen Balzaktivität und Testosterontitern bei männlichen Zebrafinken

The determination of hormone titers in small plasma volumes by radioimmunoassay makes it possible to demonstrate the mutual relationship between testosterone titers and sexual behaviour. Testosterone titers were measured after courtship tests in male Zebra Finches to determine whether these levels are influenced by sexual behaviour. The results show that immediately after a courtship test there is a significant difference in hormone levels between sexually experienced and inexperienced birds. Sexual experience can also be shown to influence baseline testosterone titers in male Zebra Finches: experienced ♂♂ have a high baseline level while inexperienced ♂♂ have a low baseline level. In two other behaviour patterns, undirected song and courtship song, it could be demonstrated, that the amount of these behaviours shown is linearly correlated with the amount of testosterone in the blood plasma. Both song types have different hormonal threshold values. The comparison of testosterone titers between different treatment groups can only be made if the groups are maintained under identical conditions, since housing conditions appear to have a very marked influence on testosterone titers. The mechanism of action of testosterone in sexual behaviour is discussed.