Effect of late winter food addition on numbers and movements of snowshoe hares

Summary Peak (1980) and early decline (1981) populations of snowshoe hares were supplied with extra food in late winter to test the hypothesis that snowshoe hare populations are limited by food supply. Food supplemented populations increased through immigration in both years but the response was more pronounced in the early decline population. Animals supplied with extra food lost less weight, had higher survival in some cases, and males began to breed earlier. Immigrants to the food addition area were of two types: those that established home ranges on or near the area and those that spent only a brief time there before returning to their initial range. The possibility that these latter individuals were prevented from remaining on the food grid by residents is discussed. Results indicate that food supply is one factor that can limit peak and declining populations of snowshoe hares but the relation of spacing behaviour to food supply and numbers must also be considered.     

The effect of supplementary feeding upon the demography of a population of woodmice Apodemus sylvaticus, living on a system of maritime sand-dunes

The woodmouse is a characteristic rodent of deciduous woodland but it also lives on maritime sand-dunes. The population density of woodmice on sand-dunes is much lower than in woodland. Hue we test the hypothesis that this difference is due to the fact that woodland provides substantially more food than do sand-dunes. Our experimental approach was to provide supplementary food (wheat grain) to a sand-dune population for a period of 22 months and to compare demographic responses with a control population.
The supplemented population increased rapidly and reached a size 6–7 times that ofthe control population. The overall annual pattern of changes in density were similar in both populations with minimum numbers in late spring, maximum numbers in autumn and a loss of individuals over the winter. The woodmice receiving supplementary food bred earlier and for longer than did the control mice.     

Direct and correlated responses to selection for larval ethanol tolerance in Drosophila melanogaster

Ethanol is an important larval resource and toxin for natural Drosophila melanogaster populations, and ethanol tolerance is genetically variable within and among populations. If ethanol‐tolerant genotypes have relatively low fitness in the absence of ethanol, as suggested by the results of an earlier study, genetic variation for ethanol tolerance could be maintained by variation in ethanol levels among breeding sites. I selected for ethanol tolerance in large laboratory populations by maintaining flies on ethanol‐supplemented media. After 90 generations, the populations were compared with control populations in egg‐to‐adult survival and development rate on ethanol‐supplemented and unsupplemented food. When compared on ethanol‐supplemented food, the ethanol‐selected populations had higher survival and faster development than the control populations, but on unsupplemented food, the populations did not differ in either trait. These results give no evidence for a ‘trade‐off’ between the ability to survive and develop rapidly in the presence of ethanol and the ability to do so in its absence. The effect of physiological induction of ethanol tolerance by exposing eggs to ethanol was also investigated; exposing eggs to ethanol strongly increased subsequent larval survival on ethanol‐supplemented food, but did not affect survival on regular food, and slowed development on both ethanol‐supplemented and regular food, partly by delaying egg hatch.     

Behavioural responses to food addition by hedgehogs

We conducted a field experiment at a 4-ha sports ground in Oxford between May and August 1992 to analyse the role of learning and social organization m the short-term responses of hedgehogs Erinaceus europaeus to manipulations of food availability On six nights we uniformly distnbuted 36 'prey' (cat food chunks) twice a night in an 70 × 70 m area (the 'patch') Prey were placed at sites marked with small flags In a subsequent experiment lasting five nights, non-marked and randomly distributed prey were provided We regularly mapped the position of individuals, before, during and after both food supplementation treatments Hedgehogs showed a stable pattern of spatial utilisation of the habitat during the non-hibernation months prior to experimental perturbation Addition of food to parts of the habitat significantly and rapidly changed these patterns a) Hedgehog density increased in food supplemented pans of the habitat b) Hedgehogs learned to associate visual cues with the presence of food c) Hedgehogs learned the spatial location of patches d) Hedgehogs probably engaged in 'area restricted' searching Hedgehogs had overlapping home ranges but showed a uniform distribution within patches and avoided conspecifics at distance < 30 m The number of different individuals visiting the area decreased throughout the experiment Food addition did not significantly change the mean density of hedgehogs, perhaps because social interactions placed an upper limit on density in the areas with supplementary food     

Effects of winter food provisioning on the phenotypes of breeding blue tits

Throughout the Western World, huge numbers of people regularly supply food for wild birds. However, evidence of negative impacts of winter feeding on future reproduction has highlighted a need to improve understanding of the underlying mechanisms shaping avian responses to supplementary food. Here, we test the possibility that carry‐over effects are mediated via their impact on the phenotypes of breeding birds, either by influencing the phenotypic structure of populations through changes in winter survival and/or by more direct effects on the condition of breeding birds. Using a landscape‐scale 3‐year study of blue tits (Cyanistes caeruleus), we demonstrate the importance of nutritional composition of supplementary food in determining carry‐over effect outcomes. We show that breeding populations which had access to vitamin E‐rich foods during the previous winter were comprised of individuals with reduced feather carotenoid concentrations, indicative of lower pre‐feeding phenotypic condition, compared to fat‐fed and unfed populations. This suggests that supplementary feeding in winter can result in altered population phenotypic structure at the time of breeding, perhaps by enhancing survival and recruitment of lower quality individuals. However, supplementation of a fat‐rich diet during winter was detrimental to the oxidative state of breeding birds, with these phenotypic differences ultimately found to impact upon reproductive success. Our findings demonstrate the complex nature by which supplementary feeding can influence wild bird populations.     

An assessment of overwinter food limitation in a snowshoe hare population at a cyclic low

Snowshoe hares (Lepus americanus) undergo 8- to 11-year population cycles caused by direct and/or interactive effects of overwinter food shortage and predation. However, the demographic significance of food shortage during cyclic population lows remains unclear. I evaluated the importance of overwinter food limitation to the demography (numbers, age and sex ratios) of low-density hare populations during two winters in Manitoba. Also, I examined whether the hypothesized differences in demography of fed and unfed hare populations could be explained by altered movement patterns or social dynamics. Bimonthly live-trapping revealed that food failed to have a direct long-term effect on the number, or change in number, of hares estimated to be on the three supplemented areas, relative to three control areas. Modest numerical responses to supplementation tended to be short-term (i.e., restricted to winter) and related to pre-supplementation densities, with the study area characterized by the highest hare density displaying the strongest and most consistent response to added food. During winter the percentage of females was remarkably variable among study areas and time periods, but added food may have augmented slightly the proportion of females captured in traps. There tended to be slightly more juveniles on supplemented areas during winter periods, and this effect was strongest during the first winter (1991–1992). I found that immigration rates and percentage of hares that were considered to be transient animals were similar on supplemented and control areas, and that spatial distribution of radio-collared animals on versus off of study areas also was similar. Because the overall effect of food on hare populations was small and short-lived, and could be explained largely by small increases in survival and reproduction, I conclude that the study population was not subject to overwinter food limitation. Received: 22 February 1998 / Accepted: 12 February 1999     

Breeding seasonality and population dynamics of three rodent species in the Magamba Forest Reserve, Western Usambara Mountains, north-east Tanzania

We investigated breeding seasonality and population dynamics of three rodent species, Lophuromys flavopuncatus, Grammomys dolichurus and Praomys delectorum, in the Magamba Forest, Western Usambara Mountains, north‐east Tanzania. Capture–mark–recapture studies were conducted in 2002–2004. Reproductive conditions of males and females showed temporal variations, an indication of breeding seasonality. Animals were reproductively active between February and May. Rainfall in November–January was instrumental for the onset of breeding and continued throughout the wet season. The recruitment of new individuals born during the season led to highest population densities between end of May and August. Populations declined progressively towards the end of the dry season (September–October). Only P. delectorum showed a marked density increase during January–February, indicating greater survival and/or recruitment during the November–January rains. The study shows that despite a relatively stable environment of the forest reserve, rainfall has strong influence on reproduction and population dynamics, probably because of its effect on primary food resources.     

The relationship between body condition and the timing of implantation in pregnant Grey seals (Halichoerus grypus)

Adult female Grey seals were sampled from the Farne Islands, Northumbria at monthly intervals during 1980 and 1981. The mean date of implantation was 7 April and most females implanted between 11 March and 5 May. Sculp, core and total body weights declined most at the time of lactation in November and were lowest during February. These weights increased most rapidly during March and April; at the same time as implantation occurred. The pectoral blubber depth followed a similar pattern. Females in which the spring increase in body condition occurred earliest also had the earliest implantation. The study demonstrates a correlation between body condition and the time of implantation.     

The breeding biology of Guillemots Uria aalge on the Isle of May over a six year period

The breeding of Guillemots was studied in five areas of different breeding density and habitat type on the Isle of May in 1981-86. Prior to 1981 numbers were increasing at 5 6° per annum but during the study the rate of increase slowed down and from 1983 to 1986 numbers were fairly constant. Adult survival was high, with a mean minimum annual adult survival of 930% (s.e. = 03). Observations in 1986 suggested that the percentage return of colour-marked immature birds was low, with only l-6% and 5.5% of second and third year birds being seen. We suggest that poor recruitment was responsible for the levelling off in numbers at the colony.
The timing of laying was constant from year to year in 1981-85 but was later in 1986. It was significantly and inversely related to sea temperature the previous March. There was a consistent ranking in median laying dates amongst the areas, with area 1 (the highest density of birds) always earliest. However, there was no significant difference in synchrony between the areas. Overall breeding success was high (0–71-0-82 young fledged per pair). There was no consistent ranking of breeding success with breeding density, habitat type or laying synchrony.
The only aspect of Guillemot biology which changed significantly was the daily food intake of a chick which approximately halved during the study period. However, this reduction in food intake had no detectable effect on either the weight of chicks with wing lengths greater than 60 mm or the amount of time off-duty breeders spent at the site. Both of these parameters were still consistent with conditions being favourable in 1986.     

Population dynamics of the oriental fruit fly, Bactrocera dorsalis （Diptera： Tephritidae） in the Kunming area,southwestern China

Population dynamics of Bactrocera dorsalis Hendel （Diptera： Tephritidae） were studied through pheromone trapping over 4 years （1997, 1999, 2000, 2003） in the Kunming region, a high plateau area in southwestern China. B. dorsalis immigrates from southern Yunnan to Kunming each year, and occurs during early May through November. Annual trap captures recorded an increase in the B. dorsalis populations from May to July, when they peaked in abundance, and a decline until November. No flies were detected from November to April. The fruit flies had two generations. There was considerable overlapping due to the continuous arrival of immigrating flies during the summer months. Annual capture rates were significantly related to numbers of flies caught in July when peak captures were recorded; whereas the peak captures, in turn, positively depended on numbers of flies recorded in May, the first month of fly appearance in the current year. It suggested that the annual population abundance was mainly dependent on the size of the initial emigrating population. A daily average temperature of 18℃ was probably the threshold temperature required for the flies to undertake long-range dispersal, which partially explained the start of the fly in May each year on this high plateau. Under field conditions, the fruit flies can withstand 13℃ as a daily average temperature. No flies were recorded in any of the study years at a daily temperature colder than 10 ℃.     

Seasonal variation in numbers of eggs laid byCulex quinquefasciatus Say (Diptera: Culicidae) at Khartoum

Regular counts of the eggs ofCulex quinquefasciatus Say were recorded during the period April 1979 – March 1981. The results indicate that the lowest numbers of eggs laid were during summer months (May and June) and the highest ones were during winter months (November and January). The decline of numbers during summer was mainly due to small size of adults (0.57 mg, average wt of female). Populations flourished during the rainy season (July – October) and reached their peak in August. Bigger batches of eggs were then obtained. In winter prolongation of larval life gave rise to large-sized adults and hence bigger batches of eggs.     

Immunocompetence and its costs during development: an experimental study in blue tit nestlings

The allocation into T-cell-mediated immunocompetence was experimentally increased in 68 out of 139 nestlings by supplementary feeding methionine to half of the nestlings in 15 blue tit nests. Methionine-supplemented nestlings had an increased T-cell-mediated immunocompetence, but a reduced growth compared with control siblings. Nestlings that had low initial weights and nestlings that were supplemented with methionine had an increased mortality risk. The investment that nestling blue tits make in immunocompetence appears to be tightly controlled by survival costs paid through a trade-off between immunocompetence and growth.     

Winter severity or supplementary feeding—which matters more for wild boar?

During recent decades, wild boar have successfully colonised areas previously believed to be unsuitable for the species. Estonia lies close to the northern limit of the species range, and mast foods, which are a common natural food source for many wild boar populations, are practically absent. We hypothesised that the proportion of cultivated area and especially supplementary feeding, which is widely used in Estonia to lower the winter mortality of game species, play important roles in sustaining the local wild boar population. To determine the most important factors shaping the abundance of wild boar in a northern environment, we developed mixed models to account for variation in an index of wild boar abundance (AI) based on winter track counts. The abundance of supplementary feeding sites and mean January temperature were the most important factors determining wild boar winter abundance. We conclude that the current high local population density is sustained by intensive supplementary feeding, which has exceeded the limiting effect of harsh winters.     

The dynamics and regulation of small rodent populations in the woodland ecosystems of Killarney, Ireland

Populations of Wood mice Apodemus sylvaticus and Bank voles Clelhrionomys glareolus were studied by mark-recapture techniques in five different woodlands but concentrated on an oak Quercus petraea wood and a yew Taxus baccata wood, where food supply was also investigated. Much of the yew wood was on limestone pavement which was greatly creviced thus providing static and quantifiable cover. Indices of the intensity with which food was being searched for were obtained on all areas by seed-removal experiments.
Trappability varied within the populations and seasonally, being highest in summer. Unusually high densities of mice were recorded in the yew wood but not elsewhere; vole densities were always low. There was an inverse relationship between range length and density: mean range length in the yew wood was exceptionally low. Males generally ranged further than females, voles further than mice. Females outnumbered males in the oak wood, where cover was minimal, when the population was low. In the two areas with most cover, males outnumbered females. In a further area, where numbers were initially exceedingly low, the population consisted entirely of males for almost a year. Sexes differed in habitat preference but numbers, especially of males, were significantly correlated with cover. Voles usually bred for shorter periods than mice. Overwinter breeding and increased overwinter survival followed good seed years. Individuals recruited when food was plentiful lived longest. In seed-removal experiments rate of removal increased with shortage of natural seed.
Food and intraspecific aggression were the probable major factors in regulating population size, of mice at least. Cover probably modifies intrinsic mechanisms by reducing numbers of encounters between individuals.     

Geese and their future fortune

Wild goose populations were probably limited by winter food supplies before Man modified their winter range and effectively removed that limitation on population growth. At the same time, reduction of hunting lowered Man-induced mortality and allowed most populations to increase both in Europe and in North America.
This paper considers likely future trends, and, using the population of Barnacle Geese breeding in Svalbard as an example, suggests how numbers might be regulated in a density related manner. The Svalbard Barnacle Goose population has shown a decline in recruitment rate and an increase in the natural mortality rate as numbers have increased. Both of these are reflections of competition on the breeding grounds, though there may be some effects at other times. We suggest that most populations will eventually be limited by resources on the breeding area.
Some of the implications of changes in numbers are that pair-bond stability and breeding area philopatry are less advantageous and in time will become less pronounced as the selective value of these traits are diminished.
We argue that both for applied reasons (conservation, crop damage prediction) and for academic investigations of population processes, long-term studies are vital in the management and understanding of goose populations. A number of features of their life history make geese very suitable subjects for such studies.     

The effect of supplemental food on the growth rates of neonatal,young, and adult cotton rats (Sigmodon hispidus) in northeastern Kansas,USA

In food-limited populations, the presence of extra food resources can influence the way individuals allocate energy to growth and reproduction. We experimentally increased food available to cotton rats (Sigmodon hispidus) near the northern limit of their range over a 2-year period and tested the hypothesis that seasonal growth rates would be enhanced by supplemental food during winter and spring when natural food levels are low. We also examined whether additional food resources were allocated to somatic growth or reproductive effort by pregnant and lactating females. The effect of supplemental food on growth varied with mass and season, but did not influence the growth rates of most cotton rats during spring and winter. In winter, small animals on supplemented grids had higher growth rates than small animals on control grids, but females in spring had lower growth rates under supplemented conditions. Growth rates of supplemented cotton rats were enhanced in summer. Northern cotton rat populations may use season-specific foraging strategies, maximizing energy intake during the reproductive season and minimizing time spent foraging in winter. Adult females invest extra resources in reproduction rather than in somatic growth. Pregnant females receiving supplemental food had higher growth rates than control females, and dependent pups (≤ 1 month of age) born to supplemented mothers had higher growth rates than those born to control mothers. Increased body size seems to confer an advantage during the reproductive season, but has no concomitant advantage to overwinter survival.     

Population expansion and breeding success of Bearded Vultures Gypaetus barbatus in the French Pyrenees: results from long‐term population monitoring

Based on monitoring of Bearded Vultures over 24 years in the French Pyrenees, we assessed factors explaining temporal and spatial variations in numbers and breeding performance. The number of territorial pairs increased throughout the study period from 16 in 1994 to 44 in 2017. No significant negative trends in mean productivity (fledglings per territorial pair) were detected with increasing population size. Colonization probability increased significantly with breeding population size the previous year and with the regular provision of supplementary food in the territory the winter when colonization occurred. Colonization of new territories simultaneously increased the distribution range and local densities, but we found no effect of number of near neighbours on productivity. Pairs having bred less than 5 years together had a much lower probability of laying clutches, and higher lay rates were observed inside or close to protected areas after accounting for pair‐bond length, so productivity of territories inside protected areas was significantly higher. Nest success decreased with advanced lay date and increased with winter food abundance. Nesting failures in the study area were frequently associated with harsh weather. Additionally, disturbance by human activities was the second most important identified cause of breeding failure. The probability of failing due to disturbance was higher in western areas (where breeding areas are more accessible to humans), outside protected areas, and has increased with time. After a failure due to disturbance, there was a significantly higher probability of not producing a clutch the following year as compared with pairs that had not failed or had failed due to other causes, indicating deferred effects of disturbance. Our results show the benefits of conservation management actions, such as implementation of protected areas or designed supplementary food programmes in winter, to help range expansion. On the other hand, we did not find a significant effect of winter supplementary food on productivity. Management of feeding sites should be adapted to more specific planning, being used only in areas where natural food availability is scarce, avoiding its use close to breeding sites when juveniles disperse, and targeted mainly to help range expansion. Our results also highlight the importance of maintaining or enhancing good populations of wild ungulates and regulating human activities around nesting sites of this threatened species.     

Winter Survival of Meloidogyne incognita in Six Soil Types

Winter survival of Meloidogyne incognita in six soil types (Fuquay sand, Norfolk loamy sand, Portsmouth loamy sand, muck, Cecil sandy clay loam, and Cecil sandy clay) was determined in microplots at one location from November 1981 to May 1982 and from November 1982 to March 1983. Survival, based on second-stage juveniles (J2) of M. incognita, from November 1981 until May 1982 ranged from 1% in the muck soil to 6% in a Cecil sandy clay loam, but survival rates were much higher the next year following a winter with higher average temperatures. Survival rates of J2 from November to March ranged from 20 to 40% the first winter and from 38 to 87% the second. Soil type did not have a striking effect on the overwintering capabilities ofM. incognita. There were no differences between clay and sand soils, whereas survival of J2 in the muck tended to be lower than in the mineral soils.     

Effects of density, climate, and supplementary forage on body mass and pregnancy rates of female red deer in Spain

The influence of short- and long-term (cohort) effects of climate and density on the life-histories of ungulates in temperate regions may vary with latitude, habitat, and management practices, but the life-histories of ungulates in the Mediterranean region are less well known. This study examined the short- and long-term effects of rainfall and absolute density on hinds in two of the southernmost populations of red deer (Cervus elaphus hispanicus) in Europe. One population received supplementary forage. Unlike more northerly latitudes, where red deer hinds lose body mass in winter as a result of adverse weather, in the Spanish populations, hinds did not lose body mass. Hinds in the population that received supplementary forage were heavier and more likely to become pregnant than were the hinds in the unsupplemented population. The likelihood of pregnancy occurring was strongly influenced by hind body mass; the proportion of yearlings that became pregnant was consequently lower in the unsupplemented population than in the population that received supplementary forage. Cohort effects on hind body mass (negative for density and positive for rainfall at birth) and on the probability of pregnancy (negative for density at birth) were apparent only in the unsupplemented population, which implies that supplemental feeding may partially compensate for negative density-dependent factors during early growth, and that supplemented deer hinds may experience reduced selection pressures. These results reflect the particular seasonal variation in the abundance and quality of food in Mediterranean habitats. The delayed effects of climate and density at birth on adult hind body mass and the prevalence of pregnancy probably affects population dynamics and constitutes a mechanism by which cohort effects affect the population dynamics in Iberian red deer. The management of Iberian red deer populations should take into account cohort effects and supplemental feeding practices, which can buffer density- and climate-dependent effects and reduce natural selection pressures.