Large Outdoor Pens Research Articles

Social learning in a nocturnal marsupial: is it a possum-ability?

Social learning can reduce the costs associated with trial-and-error learning. There is speculation that social learning could contribute to trap and bait avoidance in invasive species like the common brushtail possum (Trichosurus vulpecula)-a marsupial for which social learning has not previously been investigated. In large outdoor pens, we presented wild-caught 'demonstrator' possums with puzzle devices containing an attractive food reward; 2 of 8 demonstrators accessed the reward the first night the puzzle was presented and another three succeeded on later nights. Meanwhile, 'observer' possums in adjacent pens watched the demonstrators for five nights and then were given the opportunity to solve the puzzle themselves; 15 of 15 succeeded on their first night (a highly significant improvement). This experiment thus provides strong evidence of social learning by common brushtail possums. Future research should investigate whether information about aversive stimuli (such as traps and toxic baits) can similarly be transmitted between possums by social learning; if so, this could have important implications for possum pest control.

1 Daily secretion patterns of thyroxine, insulin, and cortisol in non-working horses on pasture when receiving one concentrate meal per day vs. no daily concentrate

Testing of metabolic hormones such as insulin (I), thyroxine (T 4 ), and cortisol (C) has become common in equine veterinary practice as the prevalence of obesity and insulin resistance has increased. There are few reports of daily secretion patterns of these hormones, as well as how diet may impact their secretion; especially in horses on pasture. Therefore, the objective of this study was to assess the daily secretion patterns of I, T 4 , and C in non-working horses on pasture receiving 0 or 1 concentrate meals/d. Sixteen horses (13 geldings and 3 mares; 6 to 22 yr of age; no diagnosed endocrine conditions) were used in a static group comparison. Horses were housed in 1 of 2 large outdoor pens with pasture access 24 h/d. Each pen of horses had ad libitum access to Teff hay and water. One pen of horses received no concentrate [no grain (NG), n = 8] and 1 pen received 2 kg Hi-Pro WTAMU Pellet (Friona, TX) once/d [grain (G), n = 8]. The meal was fed daily at 0700 except on sample collection days, when fed at 1100. The 42-d experiment consisted of 6 7-d periods with 1 sample collection d/period. On each sample collection day, blood samples were collected via jugular venipuncture between 0800 and 1000 (AM), 1200 and 1400 (MD), 1600 and 1800 (PM) h. Data were analyzed using the MIXED procedure of SAS v. 9.4 (SAS Institute, Inc., Cary, NC). No diurnal patterns were observed for T 4 or I, but C exhibited an expected circadian secretion pattern with the greatest concentration observed in the AM and decreasing throughout the day. There was an effect of treatment on plasma T 4 , with greater ( P < 0.001) overall mean T 4 observed in NG (23.2 ± 1.3 ng/mL) compared with G (16.0 ± 1.2 ng/mL). There was an effect of the interaction of treatment, period, and time of day on plasma I ( P < 0.001), with a spike in I during the MD collection following the 1100 meal in G, while NG horses remained relatively low across all 3 collections. There was an effect of the interaction of treatment and time of day ( P = 0.036) on plasma C. Both groups of horses exhibited expected diurnal secretion patterns of C in multiple periods. Horses in the G group appeared to have a greater decrease in C from the AM to MD collection than NG horses in several periods. Results from this experiment indicate that there is no diurnal secretion pattern for T 4 or I but support the presence of the circadian rhythm of C secretion. These results also highlight the influence concentrate meals may have on the outcomes of diagnostic tests and the importance of following a standardized fasting protocol during diagnostic testing.

Effects of forestry-driven changes to groundcover and soil moisture on amphibian desiccation, dispersal, and survival.

Over 80% of amphibian species that are declining are forest dependent. Forestry practices are a major cause of forest alterations globally, and it is well documented that clearcutting can contribute to amphibian declines. However, there might be adverse effects of forestry practices other than clearcutting. For example, planting overstory trees in rows (plantations) can change groundcover microhabitats and soil moisture levels, but the effects of this common practice on amphibian populations are not well studied. We compared the impacts of common intensive pine plantation operations to naturally regenerated pine forests on the desiccation, movement rates, behavior, and survival of >900 juvenile southern toads (Anaxyrus terrestris). Pine plantations had significantly more accumulation of conifer needles and less exposed soil, herbaceous groundcover, broadleaf litter, and soil moisture than natural pine forests despite the greater canopy cover at plantations. Litter cover explained 85% of groundcover microhabitat variance among forest types and predicted minimum soil moisture levels. When toads were held in small outdoor enclosures that constrained microhabitat selection, 24-h desiccation rates and 72-h mortality were significantly greater in pine plantation than in naturally regenerated pine forest because of lower soil moisture, especially during low rainfall periods. In large outdoor pens where juvenile amphibians could select microhabitats, movement was strongly directed down slope and increased with precipitation. However, initial speeds were positively associated with pine density, likely because toads were trying to evacuate from the drier high-pine-density areas. High-intensity silviculture practices that eliminate herbaceous or vegetative groundcover, such as roller chopping and scalping, increase amphibian desiccation because planted conifers dry the upper soil layer. Our study highlights the importance of prioritizing lower intensity silviculture practices or lower pine densities to retain groundcover microhabitat that serves as amphibian refugia from dry conditions that are predicted to increase in frequency with climate change.

Head-bobbing behavior in foraging whooping cranes favors visual fixation

Many species of birds move their heads forward through a series of successive, fixed positions when walking. This unique ‘head-bobbing’ behavior stabilizes visual fields during body movement, preventing motion blur of the retinal image [1–3]. Gaze stabilization could be required for successful visual search, particularly for moving objects [4], but the time available for stabilization varies with walking speed. No direct evidence has been published showing that birds favor the stabilization phase while foraging either for moving or immobile food.

HEMATOLOGIC RESPONSES IN CAPTIVE WHITE-WINGED DOVES (ZENAIDA ASIATICA), INDUCED BY VARIOUS RADIOTRANSMITTER ATTACHMENTS

White blood cell counts, heterophil-lymphocyte ratios, and leukocyte differentials of captive white-winged doves (Zenaida asiatica) from Texas equipped with different radiotransmitter attachment packages were monitored. Doves were segregated by gender and age by males, females, and hatching year; individuals housed in 30 large outdoor pens in groups of seven. Treatments consisted of controls, glue-on transmitters, body loop harnesses, surgically implanted intracoelomic transmitters, surgically implanted subcutaneous transmitters, intracoelomic surgery without implants, and subcutaneous surgery without implants. We used multivariate analysis of variance with pen as a blocking variable and gender nested and repeated measures analysis of variance to identify differences among any of the transmitter attachment techniques and the control for dependent variables. We found no difference in blood parameters between transmitter attachment technique versus a control.

Role of a neuronal small non-messenger RNA: behavioural alterations in BC1 RNA-deleted mice

BC1 RNA is a small non-messenger RNA common in dendritic microdomains of neurons in rodents. In order to investigate its possible role in learning and behaviour, we compared controls and knockout mice from three independent founder lines established from separate embryonic stem cells. Mutant mice were healthy with normal brain morphology and appeared to have no neurological deficits. A series of tests for exploration and spatial memory was carried out in three different laboratories. The tests were chosen as to ensure that different aspects of spatial memory and exploration could be separated and that possible effects of confounding variables could be minimised. Exploration was studied in a barrier test, in an open-field test, and in an elevated plus-maze test. Spatial memory was investigated in a Barnes maze and in a Morris water maze (memory for a single location), in a multiple T-maze and in a complex alley maze (route learning), and in a radial maze (working memory). In addition to these laboratory tasks, exploratory behaviour and spatial memory were assessed under semi-naturalistic conditions in a large outdoor pen. The combined results indicate that BC1 RNA-deficient animals show behavioural changes best interpreted in terms of reduced exploration and increased anxiety. In contrast, spatial memory was not affected. In the outdoor pen, the survival rates of BC1-depleted mice were lower than in controls. Thus, we conclude that the neuron-specific non-messenger BC1 RNA contributes to the aptive modulation of behaviour.

Long-term monitoring of hippocampus-dependent behavior in naturalistic settings: mutant mice lacking neurotrophin receptor TrkB in the forebrain show spatial learning but impaired behavioral flexibility.

Previous behavioral studies (Minichiello et al., Neuron 1999;24:401-414) showed that mice deficient for the TrkB receptor in the forebrain were unable to learn a swimming navigation task with an invisible platform and were severely impaired in finding a visible platform in the same setup. Likewise, additional behavioral deficits suggested a malfunction of the hippocampus and proximally connected forebrain structures. In order to discriminate whether the behavioral impairment was caused either by deficits in spatial memory and learning, or alternatively by loss of behavioral flexibility, 8 trkB mutant, 13 wild-type, and 22 heterozygous mice were implanted with transponders and released for 21 days into a large outdoor pen (10 x 10 m). The enclosure contained 2 shelters and 8 computer-controlled feeder boxes, delivering food portions for every mouse only during their first visit. Every third day, mice received food ad libitum inside the shelters. All mice learned to patrol the boxes correctly within a few days. However, significant differences emerged during those days with free food available. Wild-type mice remained inside the shelters, while all homozygous mutants continued to patrol the boxes in their habitual way, the heterozygous mutants showing intermediate scores. These and previous data suggest that one of the natural functions of the mouse hippocampus is to comediate behavioral flexibility, and that TrkB receptors might play an essential role in maintaining the neuronal short-term plasticity necessary for this capacity.

Trappability of Wild House Mice (Mus domesticus) in Large Outdoor Pens: Implication for Models of t-complex Gene Frequency

-Wild house mice (Mus domesticus) are commonly heterozygous (+/t) for a genetic mutation referred to as a t-haplotype, in the t-complex of chromosome 17. Considerable debate has been concerned with the factors controlling the frequency of heterozygotes in wild populations. However, differential trappability of heterozygous and wildtype (+/+) mice could seriously affect this estimate. We examined the relative propensity of +/t and +/+ mice to enter Sherman live traps placed in large outdoor pens. Overall, males are more likely to enter traps than are females. Additionally, more aggressive males are more likely to enter traps than are less aggressive ones. However, there was no statistically significant effect of male t-complex genotype on capture rate. In contrast, +/t females were significantly less likely to enter live traps than their +/+ counterparts. Trapping bias favoring +/+ over +/t females could result in a small (ca. 10%) underestimate of the frequency of t-haplotypes among wild mice.

Does the Siberian chipmunk respond to the snake by identifying it?

Siberian chipmunks were presented with snakes and 4 control animals (tortoises, frogs, eels, quails) in a large outdoor pen to examine whether the snakedirected behavior of the chipmunk is a response to identifying the snake or simply an exploratory behavior toward generally strange objects. The animals were presented to chipmunks in 3 manners; tethered, anesthetized, and in perforated opaque boxes and in wire netting boxes. In “tethered” and “anesthetized”, chipmunks responded significantly more intensively to snakes than to other animals. When the animals were presented in the boxes, that is, when chipmunks could perceive only olfactory stimulus from the animals, they also showed the strongest response to snakes. The results suggest that 1) snake-directed behavior of chipmunks is not a general exploratory response toward strange objects but a response to identifying the snakes, and that 2) olfaction is an important cue for the chipmunks to identify snakes.

Establishment of dominance in domestic Norway rats: Effects of the degree of captivity and social experience

The effect of the level of captivity and prior social experience on the establishment of dominance was examined in 16 colonies of albino rats. Males were assigned to one of four treatment groups: aggressive experience, defeat experience, exposure to electric shock, and controls. Following treatment, colonies of four males were established for 12 days in one of three different captive setings: a large outdoor pen, an indoor pen, or laboratory group cages. Effects of treatment were minimal; however, the degree of captivity significantly affected the display of aggression and the establishment of dominance relationships. In the two pen settings, attacks were more frequent and dominance relationships were established in six of eight colonies. Attacks in the laboratory cages occurred almost exclusively during the first 2 days, and no dominance relationships were established in any of eight laboratory cage colonies.

Degrees of captivity and aggressive behavior in domestic Norway rats

Six categories of aggressive behaviors were studied in groups of domestic rats observed for 3 months and in three settings of varying degrees of captivity. In the least captive situation, a large outdoor pen, aggression frequently took a wild-type form (aggressive side postures, biting attacks) and infrequently took a “playful” form (pins, aggressive grooms) relative to aggression shown by rats in the most captive situation, laboratory cages. Rats housed in an intermediate degree of captivity showed intermediate levels of both serious and playful types of aggression. Male and female intruders were attacked by residents of all three settings, most seriously in the outdoor pen. These results indicate that captivity may have a powerful effect on the form of aggression shown by domestic rats.

Dynamics of Grit Selection and Retention in Captive Mallards

The role of grit selection and retention on mortality rates of captive mallards (Anas platyrhynchos) that had ingested lead shot was evaluated in a series of experiments. The calculated rate of grit retention was determined from the negative exponential relationship between the number of marked grit particles in the gizzard and time. Grit consumption, the primary rate-determining step of grit retention, was significantly (P < 0.01) affected by diet, sex, season, mineral composition, and size of particles. Peak grit ingestion by males occurred in the fall, and in females in spring. Ducks maintained on a corn diet consumed twice as much grit as ducks maintained on commercial duck pellets. When offered grit particles between 0.42 and 4.75 mm in diameter, both sexes selected grit particles between 0.84 and 2.00 mm. In spring, females selected oyster shell and sandstone grits over granite, calcium, and quartzite, whereas males preferred sandstone to all other grit types. J. WILDL. MANAGE. 45(1):64-73 Avian species require grit for food digestion (McIlhenny 1932, Leopold 1933) and as a source of trace minerals (Sadler 1961, Harper and Labisky 1964, Kopishke 1966). Bellrose (1959) reported that the time of lead-shot retention was important in determining the degree of mortality suffered by a group of lead-ingesting individuals. Beer and Stanley (1965) postulated that lead and grit interacted, and when excess grit was ingested it was passed and in some instances took the lead shot with it. Bellrose (1975) stated that the size of the lead particle influenced its rate of passage. The kind of grit (calcium) has been shown to lower the mortality of experimentally dosed mallards (Godin 1967, Longcore et al. 1974). The objectives of this study were to identify the factors affecting grit selection and retention in mallards and the role of grit in shot ingestion and retention. I am indebted to the Max McGraw Wildlife Foundation and the College of Agriculture and Life Sciences, University of Wisconsin, Madison, for financial support. The assistance of the foundation staff and G. V. Burger's help with the manuscript are appreciated. I also thank the faculty and graduate students of the Department of Wildlife Ecology, University of Wisconsin, Madison, for their help and suggestions. In particular I acknowledge the guidance and support of R. A. McCabe. METHODS AND MATERIALS Ten experiments were conducted, 9 of which took place within specially constructed pens designed to prevent access to grit. The pens were 2.4 x 2.4 x 1.5 m, with a floor of woven hardware cloth (1-cm mesh) raised 0.6 m above the ground. Six pens were constructed within 1 large outdoor pen. Sheets of corrugated fiberglass were placed 5 cm beneath the floor and inclined toward the front of each pen so that runoff drained into a collection trough. All pens were equipped with a plastic pool 38 cm deep and 75 cm in diameter. A grit feeder (Sadler 1961) was provided inside each pen. A preliminary study was conducted to obtain variance estimates for the computation of sample sizes and types of marker grit. A sample of 10 ducks/experime tal group was determined to be adequate. The best marker grit was green quartzite. Four grit-particle sizes were used: 10 (2.01-4.76 mm), 20 (0.85-2.00 64 J. Wildl. Manage. 45(1):1981 This content downloaded from 157.55.39.56 on Tue, 18 Oct 2016 04:35:10 UTC All use subject to http://about.jstor.org/terms GRIT SELECTION IN MALLARDS * Trost 65 mm), 30 (0.60-0.84 mm), and 40 (0.43-0.59 mm); size was measured as the largest diameter of the smallest cross-section of each particle. Ducks were banded and randomly assigned to treatment groups. At 48-hour intervals, measurements were made of grit and feed consumed by each experimental group, and fecal material was collected. The pens were then washed to prevent reingestion of any marker grit remaining. Fecal materials were washed into large metal containers and agitated to liquefy the fecal pellets. The effluent was poured off and the sediment dried overnight at 120 C. The dried sediment was then crushed lightly using a mortar and pestle and rewashed. After a final drying the grit was sorted and weighed. During the preliminary experiment, a minimum acclimatization period of 2 weeks was necessary to attain a steady consumption of food and grit. In all subsequent experiments, ducks were acclimated to their pens for 2 weeks prior to

Herpesvirus sylvilagus IN COTTONTAIL RABBITS: EVIDENCE OF SHEDDING BUT NOT TRANSPLACENTAL TRANSMISSION

Herpesvirus sylvilagus was inoculated into five cottontail rabbits (Sylvilagus floridanus) at various stages of pregnancy; they subsequently had litters in the laboratory. Three other cottontails chronically infected with the virus were bred and bore young in large outdoor pens. Thirty-four living neonates and dead fetuses were weighed, measured and aseptically necropsied. A total of 31 liver, spleen and kidney samples, 16 lymph node, 28 heart and 10 brain samples were collected and processed for inoculation into rabbit kidney cell cultures to attempt virus isolation. Virus was not detected in the 147 tissue samples tested. Pre-conception viremias ranged from 10-21 plaque-forming units per 0.5 ml. Virus isolation was attempted from 26 oral and lacrymal, 23 genital, nine urine and fecal, and four milk and male ejaculate samples from eight infected rabbits. Virus was recovered from two salivary samples from the same rabbit. Triamcinolone acetonide administered daily for four days to five rabbits did not stimulate excretion of virus.

Long-term effects of social rehabilitation in rhesus monkeys

A group of 19 rhesus monkeys was assembled and observed in a large outdoor pen. Five experimental groups were present: 3-year-old mother-peer reared monkeys, surrogate-rehabilitated isolates, socially-rehabilitated isolates, surrogate-peers (who had served as “therapists” for the preceding group), and 1-year-old mother-peers. The major results indicated first, that the surrogate-rehabilitated isolates played socially significantly less than both mother-peer groups, and second, that the group as a whole seemed to display an abnormally low overall level of behavior. Possible interpretations and theoretical implications are discussed.

Bioenergetics of a Woodlot Gray Squirrel Population

The gray squirrel (Sciurus carolinensis) population in an isolated 3.2-ha, overmature wood- lot was estimated by trap-retrap procedures for each of the 4 seasons of I year, September 1971- September 1972. The energy requirements of these gray squirrels were extrapolated from the caloric intake determined from gray squirrels housed in large outdoor pens. Mean dry weight production and caloric values of the 20 most important foods available to squirrels were determined from samples col- lected on a seasonal basis, and the energy flow through the woodlot squirrel population was calcu- lated. The average daily food consumed by the penned squirrels varied from 50.9 g/W?75 (W = live weight in kg) for subadults to 55.6 g/W.'75 for adults and 60.7 g/W75 for juveniles. These squirrels voluntarily restricted their food in the winter. Our wild population had a seasonal average of 15.7 squirrels/ha, or 0.71 g/m2/season, and an average energy density of 1.25 kcal/m2/season. The food energy available to this population during the year was 282.75 kcal/m2/year. Of this energy, 32.0 per- cent was ingested and 23.9 percent was metabolized, of which 23.6 percent was utilized for mainte- nance and only 0.3 percent for production. Our investigations indicated that this sciurid, with a wide food-base of both reproductive and vegetative plant parts, efficiently utilized the food available. Both the utilization efficiency of food energy and the energy density of this squirrel population were greater than has been reported for other small mammals.

Interaction and Habitat Selection in the Mice Apodemus Flavicollis and A. Sylvaticus

Males of Apodemus flavicollis (Melchior) and A. sylvaticus (L.) were given a choice between a grassland and a beech-wood habitat. Newly caught animals were tested alone or together in three types of enclosures ranging from small indoor to large outdoor pens. Distributions were recorded by direct observation, automatically by an event recorder, and by trapping. Interactions and other behavioural traits relevant to habitat selection were studied. In all three types of enclosures, the relative distribution pattern of the two species was such that A. flavicollis occurred about as much in both habitats, whereas A. sylvaticus occurred more in the grassland. A. flavicollis was also more active in a novel environment and showed a stronger tendency to climb. In interspecific encounters this species clearly dominated A. sylvaticus, generally in a passive way. It was less aggressive in intraspecific encounters than A. sylvaticus. The presence of A. flavicollis inhibited activity of A. sylvaticus and increased its occurrence in the grassland. When tested together the two species tended to segregate vertically.

Viability of Wild Meadow Voles Under Various Conditions of Population Density, Season, and Reproductive Activity

Wild meadow voles, Microtus pennsylvanicus, from four undisturbed populations were studied to learn the influence of population density, season, and reproductive activity on survival time in acute stress and on gland weights. Survival time in cold water was longer in winter. Survival time showed no correlation with population density in fall samples taken from very sparse to very dense populations. Thymus weights were lower in breeding voles and lower in winter. Adrenal weights were greatly influenced by reproductive activity, being increased in females and decreased in males. The results of the two survival tests used on one population, fasting—dehydration and cold water, showed different trends of change during two winters. In two experiments covering two to four months, the effect of density on survival time and gland weights was studied by manipulation of vole numbers on an island and in large outdoor pens, to create populations of high and low density. The average survival time in cold water and the gland weights showed no differences related to density. Analysis of the correlations between survival time in cold water and gland weights indicated that the adrenal, thymus, and spleen weights were not useful as indicators of viability. It is postulated that changes in mortality rates as a result of decreased viability due to dense population conditions play a minor role in fluctuations of rodent numbers.