A yardstick for measuring populations of small rodents

(1) Six-monthly trappings (summer and winter) were done between 1952 and 1969 of Wood mice (Apodemus sylvaticus) and Bank voles (Clethrionomys glareolus) in Wytham Woods, near Oxford. One hundred and fifty Longworth live traps were used on two 2-acre grids in oak-ash-sycamore woodland. (2) The traps were pre-baited for 48 hours and then set. The catch was examined on the evening of the same day and on the following morning. The total of animals caught during the 24 hours was used as an index to the actual numbers present. Animals retrapped in the morning (identified by a simple method of marking) were omitted from the total. (3) Between 1969 and 1972 the same procedure was used but trapping, evening and morning, was continued for 3-4more days until some 75–80% of the catch consisted of marked animals. (4) This enabled estimates to be made of the actual numbers of voles and mice present at each trapping and so to assess the proportion of the total present which was caught ring the first 24 hours. (5) These estimates were made by (Method la) a straight Lincoln Index, (Method lb) a Lincoln Index method as modified by Hayne (1949) and (Method 2) by Hayne's trap-out method. Over six trappings the estimates by these methods showed reasonable agreement. (6) Comparison of the index trapping (i.e. the numbers caught during the first 24 hours) with the estimates of the total numbers present showed that, on all occasions, more than half of the mice and voles present entered the traps during the first 24 hours. With Bank voles there was a tendency for about half of them to be trapped during this time during the winter and about three-quarters of them during the summer. (7) With Wood mice the figures are more variable but, again, never less than half were trapped during the first 24 hours and, on some occasions, nearly the whole of the population. (8) These results show that reasonably accurate estimates of the numbers of these rodents can be achieved within 3–4 days' trapping (estimates that can be cross-checked by different methods) by using a high density of traps (see (1) above). Furthermore, trapping for 24 hours only will always catch at least half of the population present and, on occasions, considerably more than half.     

Studies on the effects of bait and sampling intensity on trapping and estimating Wood mice, Apodemus sylvaticus

The effects of baiting a Longworth trap with whole oats and the density of traps on an area, or sampling intensity, on trapping and estimating Wood mice were studied on two neighbouring woodland plots in November 1971. Standard capture-mark-recapture (CMR) methods were used for two weeks followed by five nights of removal trapping.
The presence of bait significantly increased the likelihood of capturing marked and unmarked animals. By increasing the sampling intensity a greater proportion of the population was sampled, although the number of animals captured per trap night decreased. These results have been related to the "effective" number of traps on an area.
Observations on population structure, weather, movement and capturing marked and unmarked animals have been made. CMR population estimates closely resembled the cumulative number of individuals captured in each study and were for the main part lower than the estimates from the removal trapping carried out at the end of the studies.     

Population ecology of the Rice rat (Oryzomys palustris) in a coastal marsh

Rice rats were studied for four years by grid trapping in a tidal marsh on the northern Gulf of Mexico. Preliminary trapping indicated that marshes are preferred over other coastal habitats. Population densities fluctuated from spring lows of about 2/ha to highs of about 25/ha in the autumn and early winter. Reproduction occurred throughout the year, the major season being late spring to late autumn. Recruitment of juveniles was at a maximum from May to September. Males were more abundant than females in population samples, and had a higher mean body weight. This was because weight classes of 40 g and below were slightly skewed in favour of females and weight classes above 40 g heavily favoured males. The survival rate was low, with less than 20% of animals marked remaining on the grids for more than three months. Maximum longevity was 24 months. Results are compared to those of previous studies done on an offshore island and in the Florida everglades.     

Different Forms of Vigilance in Response to the Presence of Predators and Conspecifics in a Group-Living Mammal, the European Rabbit

In group‐living mammals, the major functions of vigilance are to detect the presence of predators and to monitor the movements of conspecific competitors, i.e. of potential opponents in agonistic encounters. The minimum distance to such a conspecific competitor that an animal considers safe is usually lower than to a predator, whereas the frequency of encounters with conspecifics is higher. Therefore, the acquisition of information about a predator or about a conspecific could lead to the existence of at least two different modes of vigilance behaviour. The aim of the present study was to describe and compare different forms of vigilance behaviour that European rabbits, Oryctolagus cuniculus, display in anti‐predator and social contexts. We conducted an observational study on individually marked animals from a field enclosure population. We recorded social interactions of the animals, the presence of aerial predators (common buzzard Buteo buteo), and the vigilance behaviour of the rabbits. We distinguished between two forms of vigilance of different intensity: subtle and overt. The frequencies of both forms of vigilance displayed by the rabbits differed significantly in occurrence, duration, and distribution over time. Females and males showed higher frequencies of overt but not subtle vigilance when buzzards were present. In contrast, the presence of conspecifics in close proximity affected the display of subtle but not overt vigilance: males increased the frequency of subtle vigilance when other males were close. Females increased subtle vigilance in proximity of males and females; however, this effect was only apparent in females with a more unstable social situation. In conclusion, European rabbits differentially increased two different forms of vigilance behaviour in social and anti‐predator contexts.     

Differential trappability of small mammals in three habitats of Southeastern Brazil.

We compared the trappability of marked and unmarked individuals in species of marsupials and rodents of three tropical assemblages of small mammals in Brazil. Two studies used trapping grids, one in cerrado and the other in an Atlantic forest reserve, whereas the study in a rural area used transects. In the two studies using trapping grids, marked animals were frequently more trappable than unmarked ones, but in some species this difference was not significant. In the rural area, marked and unmarked animals did not differ significantly. The number of recaptures per resident animal was higher in the two studies using trapping grids than in the rural area where transects were used. Differences in trappability between the three studies might have been caused by differences not only in trapping design (grids vs. transects), but also in the type of trap used, bait, and habitat. Although differential trappability tends to be considered the rule in small mammals, these results suggest that trappability of marked and unmarked animals may be specific for the particular combination of sampling design, field methods, and habitat under study.     

Personality, habitat use, and their consequences for survival in North American red squirrels Tamiasciurus hudsonicus

Personality affects many aspects of an individual's behaviour, life history and fitness, and has been shown to be moderately heritable in wild populations. Correlations between personality and risk‐taking that lead to life history tradeoffs could act to maintain variation in personality within a population, but this has not yet been tested. In this study, we used females from a marked population of North American red squirrels in Kluane, Yukon, to determine whether personality predicts risk‐taking in the wild, and whether these risk‐taking behaviours result in life history tradeoffs. We measured personality in open field and mirror image stimulation tests and extracted two traits, activity and aggressiveness, using principal component analysis and mixed model techniques. Using trapping records for individuals from February to September 2005, we obtained three measures of risk‐taking: the number of trapping events, the number of different trapping locations, and the maximum distance between the home territory and a trapping event. We used GLMs to determine whether the activity and aggressiveness of individuals are related to these risk‐taking behaviours, and found that active squirrels were trapped significantly more frequently and at a greater number of locations. There was also a significant interaction between activity and aggressiveness to affect the maximum capture distance. To determine if there are fitness tradeoffs associated with these risk‐taking behaviours, we examined female bequeathal behaviour and survival. Bequeathing a territory increases offspring probability of overwinter survival, and we found that an increasing number of trapping locations was associated with an increasing tendency to bequeath. Active females were less likely to survive until the following spring. Risk‐taking is therefore predicted by personality in this population, and they affect both survival and territorial bequeathal. These fitness tradeoffs may therefore lead to the maintenance of variation in personality.     

Quantifying the Shelter Rabbit Population: An Analysis of Massachusetts and Rhode Island Animal Shelters

Scholarly work on the nonhuman animal shelter population has widely focused on cats and dogs. As a result, little is known about the population dynamics of domestic rabbits (Oryctolagus cuniculus) in shelters. The records from 4 companion animal shelters in Massachusetts and Rhode Island were analyzed to describe these dynamics. A majority of the rabbits at the 4 shelters were surrendered by their caregivers, were between 1 and 6 years old, and were unaltered at the time of intake. The most common reasons for surrender were the caregivers' inability to care for the rabbits or a lack of interest in doing so. Over half of the total rabbit population was subsequently adopted and the overall live release rate (percentage of rabbits leaving the shelter alive) was 75.54%. In some cases, the use of a foster care system was correlated with a decrease in the euthanasia rate. The results from this study will help the sheltering field clarify the scope of the problem of homeless rabbits.     

Demography,density, and survival of an endemic and near threatened cottontail<Emphasis Type="Italic">Sylvilagus cunicularius</Emphasis> in central Mexico

A 3-year live trapping investigation was carried out in a temperate forest in central Tlaxcala, México from 2002 to 2004. During a total of 504 trap nights, 87Silvilagus cunicularius Waterhouse, 1848 individuals were captured and marked, and age-specific survival models using demographic parameters were tested using the JOLLYAGE program. We evaluated population density of this species over a 1-year period. The age structure of the population varied among years, and the proportion of adults was relatively constant among years, whereas the proportion of juvenile showed high fluctuations. The sex ratio of juveniles that were recaptured as adults, did not differ from unity neither did the sex ratio for adults. We found no sex bias among cottontails during all 3 years of the study. When data for both sexes were combined, mean survival probability of juveniles was lower than that of adults. Although our line transect counts showed a mean density of 27 ± 5.4 individuals per km², the obtained results from trapping suggests that this species is low in abundance at La Malinche. Further studies are needed to evaluate demographical aspects of this species at different protected and unprotected areas to obtain robust information about their status.     

Eradication of Feral Cats (Felis catus) from Gabo Island, south-east Victoria

Summary Concerns about the effects of predation by Feral Cats ( Felis catus ) on native fauna, particularly breeding seabirds, precipitated a decision in 1987 to control and eventually eradicate cats from Gabo Island. The size of the population prior to control was at least 30 animals. A control programme, undertaken between 1987 and 1991, centred on shooting, trapping and an extensive 1080 poison-baiting programme. Trapping and shooting were ineffectual. Poisoning was the most successful and effective technique for the rapid and widespread reduction in the Feral Cat population on Gabo Island. The effectiveness of dead 1-day-old chickens as a poison carrier was demonstrated. Effective poison baiting was attributed to bait selection and strategic timing of baiting to periods when prey was at low levels. Outcomes from the trapping programme and post-control monitoring strongly suggested that the cat population had been reduced to only two or three animals, possibly of the same sex. Monitoring between 1992 and 1998 failed to record any evidence of cats, indicating that the cats remaining after poison baiting had been unable to sustain a viable population. On the basis of the available evidence, Feral Cats appear to have been successfully eradicated from Gabo Island.     

Long distance movement of Bank voles and Wood mice.

Between November 1963 and October 1965 the long distance movements of Bank voles and Wood mice within an almost isolated 26 ha deciduous woodlot were studied by live trapping at approximately monthly intervals. Dispersal was most marked in juvenile Bank voles where most of the males and about half the females under 13 g, when released and later recaptured, had dispersed.
Dispersal of juvenile Wood mice did not occur after September, before which time the evidence was sparse and inconclusive. It was estimated that about 6% of adult maleand 2% of adult female Bank voles dispersed. Little dispersal of adult Wood mice took place.
The term 'transient' is discussed. True transients in the "once-caught' category are thought to be few. There was no evidence that the trappable population of either species included a significant number of non-resident individuals.     

Estimating myostatin gene effect on milk performance traits using estimated gene content for a large number of non-genotyped cows

The objective of this study was to estimate the myostatin (mh) gene's effect on milk, protein and fat yield in a large heterogeneous cow population, of which only a small portion was genotyped. For this purpose, a total of 13 992 889 test-day records derived from 799 778 cows were available. The mh gene effect was estimated via BLUP using a multi-lactation, multi-trait random regression test-day model with an additional fixed regression on mh gene content. As only 1416 animals, (of which 1183 cows had test-day records) were genotyped, more animals of additional breeds with assumed known genotype were added to estimate the genotype (gene content) of the remaining cows more reliably. This was carried out using the conventional pedigree information between genotyped animals and their non-genotyped relatives. Applying this rule, mean estimated gene content over all cows with test-day records was 0.104, showing that most cows were homozygous +/+. In contrast, when gene content estimation was only based on genotyped animals, mean estimated gene content over all cows with test-day records was with 1.349 overestimated. Therefore, the applied method for gene content estimation in large populations needs additional genotype assumptions about additional animals representing genetic diversity when the breed composition in the complete population is heterogeneous and only a few animals from predominantly one breed are genotyped. Concerning allele substitution effects for one copy of the 'mh' gene variant, significant decreases of -76.1 kg milk, -3.6 kg fat and -2.8 kg protein/lactation were obtained on average when gene content estimation was additionally based on animals with assumed known genotype. Based on this result, knowledge of the mh genotypes and their effects has the potential to improve milk performance traits in cattle.     

cameratrapR: An R package for estimating animal density using camera trapping data

• 1.Camera trapping plays an important role in wildlife surveys, and provides valuable information for estimation of population density. While mark-recapture techniques can estimate population density for species that can be individually recognized or marked, there are no robust methods to estimate density of species that cannot be individually identified.
• 2.We developed a new approach to estimate population density based on the simulation of individual movement within the camera grid. Simulated animals followed a correlated random walk with the movement parameters of segment length, angular deflection, movement distance and home-range size derived from empirical movement paths. Movement was simulated under a series of population densities. We used the Random Forest algorithm to determine the population density with the highest likelihood of matching the camera trap data. We developed an R package, cameratrapR, to conduct simulations and estimate population density.
• 3.Compared with line transect surveys and the random encounter model, cameratrapR provides more reliable estimates of wildlife density with narrower confidence intervals. Functions are provided to visualize movement paths, derive movement parameters, and plot camera trapping results.
• 4.The package allows researchers to estimate population sizes/densities of animals that cannot be individually identified and cameras are deployed in a grid pattern.

     

Feedback in the rabbit's central circadian system, revealed by the changes in its free-running food intake pattern induced by blinding, cervical sympathectomy, pinealectomy, and melatonin administration.

Long-term records of the number of food approaches per 30 min were obtained from 16 rabbits in constant light and after blinding. Optic nerve sectioning usually resulted in a shortening of the free-running period (tau; mean reduction = -0.26 hr) of the oscillator governing the rabbit's food intake pattern. Subsequent resection of both superior cervical ganglia always reduced this tau (mean = -0.41 hr), and it could be further shortened (mean = -0.24 hr) by chronic administration of melatonin. These observations led to experiments in which the food intake of 15 blinded rabbits was recorded before and after pinealectomy. This always resulted in a lengthening of tau (mean = +0.27 hr), which was never seen after subtotal or sham pinealectomy in 10 other blinded animals (mean = -0.05 hr). Sympathectomy also reduced tau (mean = -0.50 hr) in the pinealectomized rabbits, whereas it induced a smaller reduction (mean = -0.29 hr) after sham pinealectomy. These results, together with previous observations on the effect of sympathectomy on the retinal "dark" discharge and on the influence of the latter upon the food intake pattern, indicate that the cervical sympathetic nerves may form part of three feedback loops for the rabbit's central circadian system. These have separate postganglionic pathways; there are also differences in the circadian phasing of their activities and in their effects on tau.     

A registry for exposure and population health in the Altai region affected by fallout from the Semipalatinsk nuclear test site

A registry of the rural population in the Altai region exposed to fallout from nuclear tests at the Semipalatinsk test site (STS) was established more than four decades after the first Soviet nuclear explosion on August 29, 1949. Information about individuals living in an exposed and a control area was collected using all available local sources, such as kolkhoz documentation, school registries, medical treatment records and interviews with residents. As a result, a database comprising an exposed group of 39 179 individuals from 53 Altai region villages, 6769 external and 3303 internal controls was compiled. For several settlements, effective dose estimates reached the level of 1.5 Sv, while the average effective dose estimate in the exposed group was 340 mSv. Dosimetric data, vital status information and health records gathered at rayon and village medical facilities are held in the registry. Cause-of-death information for deceased residents is obtained from death registration forms archived at the Altai region vital statistics office. At present, a follow-up of approximately 40% of the population exposed in 1949 has been done. More will be added by searching for migrants to the larger towns of the Altai region, i.e. Barnaul, Rubtsovsk and Biisk. In order to assess the influence of radiation exposure, analytical studies with a case-control design for stomach and lung cancer are currently being prepared. The number of known cases is sufficient to detect an odds ratio of 1.5 at the 95% confidence level. Epidemiological studies in populations affected by fallout from STS may be equally important to the atomic bomb survivors’ study for the direct quantification of radiation effects. The range of exposure rates experienced will extend the acute high-dose-rate findings from Hiroshima/Nagasaki towards acute and protracted lower exposures, which are more relevant for radiation protection issues. Received: 3 March 1999 / Accepted in revised form: 8 June 1999     

Trapping a local population of spruce bark beetles Ips typographus (L.): Population size and origin of trapped beetles

A method of trapping local populations of Ips typographus was investigated in the field. The size of a population emerging from a hibernation site in the forest litter was estimated using tent traps. This estimate was compared with another estimate where beetles from the population were marked and recaptured in pheromone traps. The estimate of population size with mark-recapture was much higher than the estimate with tent traps, indicating a high degree of immigration. According to calculations only a minor part (less than 20%) of the beetles caught in the pipe traps originated in the local population. Re-emerging parent-adults were marked and released during the second flight period. The recapture rate was 29.8%, almost the same as during the first flight. Immigration during the first and second flight periods was estimated to be of similar magnitude. The results show that it is difficult to suppress local populations of highly mobile bark beetles by trapping.     

Pinealectomy Decelerates the Circadian Food Intake Rhythm of Cervically Sympathectomized Rabbits

Long-term records of the free-running food intake rhythms were obtained from 26 young adult blinded rabbits that were subjected in the course of recording to bilateral superior cervical ganglionectomy (sympathectomy). This always resulted in acceleration of the rhythm (mean λ r= - 0.35 h). Some 4 months afterwards, 12 rabbits were pinealectomized and after another 4 months sham pinealectomized also. In the other 14 animals, these operations were performed in the reverse order. It appeared that suctioning away part of the ventricular walls during sham pinealectomy was followed by a slight reduction in r (mean = - 0.07 h) that could be largely attributed to the spontaneous gradual reduction of r that occurred throughout all experiments. On the other hand, total pinealectomy in these already sympathectomized blinded rabbits always resulted in a substantial deceleration of the rhythms (mean λ r = + 0.23 h). These observations on blinded rabbits suggest that a sympathetically denervated pineal gland releases appreciable amounts of melatonin or of another hormone with a melatonin-like accelerating effect on the circadian pacemaker (SCN).     

Habituation in the rabbit visual cortex during development and after septal ablation

In chronic experiments on adult rabbits with injury to the septum pellucidum and on newborn rabbits the dynamics of evoked responses to repeated flashes was studied. Experimental blocking of the hippocampal theta-rhythm by electrolytic destruction of the medial septum is followed by marked facilitation of habituation of the primary responses. This process takes place twice as fast in rabbits with damage to the septum as in intact animals. Very rapid habituation of the primary responses was observed in newborn rabbits before acquiring vision and in rabbits with vision but under the age of 15–16 days, after 10–20 presentations of the stimulus. When the animals reached this age the time required for habituation increased sharply. Starting from the age of 17 days, the primary responses of the animals were just as stable as in normal adult rabbits. The significance of the hippocampal theta-rhythm as a factor preventing the development of habituation is discussed.Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 123–129, March–April, 1972.     

Immunochemical studies of ferrochelatase protein: characterization of the normal and mutant protein in bovine and human protoporphyria.

Protoporphyria is a hereditary disorder characterized by a marked decrease in the activity of ferrochelatase, the terminal enzyme in the heme biosynthetic pathway. We have prepared specific polyvalent antibodies against bovine ferrochelatase in rabbits. The specificity of the antibody preparation against ferrochelatase was demonstrated by western blot analysis and immunoprecipitation of ferrochelatase activity. The antibody also cross-reacted weakly with ferrochelatase from human mitochondria. To quantify immunoreactive ferrochelatase in tissue samples, a kinetic-based enzyme-linked immunosorbent assay (k-ELISA) was developed. Ferrochelatase activity and the level of immunoreactive protein were measured in hepatic mitochondria isolated from six normal and nine protoporphyric (homozygous) cattle. Ferrochelatase activity was less than 10% of normal in mitochondria from protoporphyric animals; the amount of immunoreactive material was equivalent to that from normal animals. Similar studies were performed with samples from three normal and two protoporphyric (heterozygous) humans. Ferrochelatase activity was decreased in protoporphyric samples (about 17% of normal, but there was no concomitant decrease in immunoreactive material. These data demonstrate that a normal amount of ferrochelatase protein is present and suggest that bovine and human protoporphyria result from point mutations in the gene encoding ferrochelatase.     

Cervical screening in Perth and Kinross since introduction of the new contract.

OBJECTIVE--To determine changes in the cervical screening service since the introduction of the new general practitioner contract on 1 April 1990. DESIGN--Analysis of computerised records of cervical screening both before and after introduction of the new contract. SETTING--General practices in Perth and Kinross Unit, Tayside. PATIENTS--A total of 30,071 women aged 21-60 on 26 general practitioner partnership lists. MAIN OUTCOME MEASURES--Percentage average of target population for cervical screening in each practice for first three quarters on introduction of the contract. RESULTS--Perth and Kinross Unit completed a computerised cervical screening call programme in July 1989, which produced an increase from 71% to 78% in the mean percentage of women aged 20-60 who had had cervical smear tests within 5.5 years. Six months after the introduction of the new general practitioner contract the mean population coverage was increased to 85% in women aged 21-60 and only four practices had not attained the 80% upper target compared with 10 on 1 April 1990. Detailed examination of randomly selected practices immediately before the new contract was introduced showed an average artificial list inflation of 4.3% in health board records when compared with practice records, a hysterectomy rate of 6.2%, and an additional 3% of women who were considered to be ineligible for smear testing due to putative virginity or illness or infirmity, or both. There was a considerable shift away from use of well woman clinics (2.7% of smears in 1990 compared with 5.6% in 1988) for taking cervical smears, potentially threatening the long term viability of the clinics. CONCLUSION--The introduction of the new contract for general practitioners has brought about a further sustained increase in population coverage for cervical screening in a small Scottish unit with a stable population, well motivated general practitioners, and a fully integrated computerised call and recall system based on the community health index. To optimise the screening service revision of the targets levels is necessary.     

Long‐term wildlife road‐kill counts in New Zealand

Abstract

We compare the number of medium‐sized animals (between rat and dog‐size) killed on repeated counts along the same 1660 km of North Island highways in 1984, 1994 and 2005 with other counts going back to 1949. Elevenmammal and 14 bird species were recorded, but Australian possums (Trichosurus vulpecula), hedgehogs (Erinaceus europaeus) and rabbits (Oryctolagus cuniculus) predominated, and pukekos (Porphyrio porphyrio), mynas (Acridotheres tristis), and Australian magpies (Gymnorhina tibicen) were the most common birds. Counts of possums, hedgehogs and rabbits ranged between 0.7 and 89 corpses/100 km, and changed dramatically over six decades. The possum count rose 80% between 1984 and 1994, but declined 60% by 2005. A possible irruption of hedgehogs is reported in 1988–89, followed by an 82% decline in their numbers between 1994 and 2005. Although rabbit hemorrhagic disease was introduced to New Zealand in 1997, rabbit road‐kill increased 59% between 1994 and 2005. The relationship between road‐kill and traffic volume indicates that roads carrying more than 3000 vehicles per day act as barriers to larger mammals, while vehicles on less busy roads are more dangerous for crossing animals. We suggest that regular counts taken at annual intervals over the same roads is a useful method for gathering information about the changing distribution and relative abundance of certain animals on a provincial or national scale and over long periods of time. Regular counts at seasonal, monthly or weekly intervals are also a rich source of information.