Absence Of Predators Research Articles

Predation has a greater impact in less productive environments: variation in roe deer, Capreolus capreolus, population density across Europe

ABSTRACTAim We aimed to describe the large‐scale patterns in population density of roe deer Caprelous capreolus in Europe and to determine the factors shaping variation in their abundance.Location Europe.Methods We collated data on roe deer population density from 72 localities spanning 25° latitude and 48° longitude and analysed them in relation to a range of environmental factors: vegetation productivity (approximated by the fraction of photosynthetically active radiation) and forest cover as proxies for food supply, winter severity, summer drought and presence or absence of large predators (wolf, Canis lupus, and Eurasian lynx, Lynx lynx), hunter harvest and a competitor (red deer, Cervus elaphus).Results Roe deer abundance increased with the overall productivity of vegetation cover and with lower forest cover (sparser forest cover means that a higher proportion of overall plant productivity is allocated to ground vegetation and thus is available to roe deer). The effect of large predators was relatively weak in highly productive environments and in regions with mild climate, but increased markedly in regions with low vegetation productivity and harsh winters. Other potentially limiting factors (hunting, summer drought and competition with red deer) had no significant impact on roe deer abundance.Main conclusions The analyses revealed the combined effect of bottom‐up and top‐down control on roe deer: on a biogeographical scale, population abundance of roe deer has been shaped by food‐related factors and large predators, with additive effects of the two species of predators. The results have implications for management of roe deer populations in Europe. First, an increase in roe deer abundance can be expected as environmental productivity increases due to climate change. Secondly, recovery plans for large carnivores should take environmental productivity and winter severity into account when predicting their impact on prey.

Sensitivity of Daphnia species to phosphorus-deficient diets

The life history of freshwater cladocerans such as Daphnia spp. is strongly affected by their environment. Factors such as temperature, food quantity and even the presence or absence of predators influence growth, reproduction and morphology of individuals. Recently, it has also become clear that the quality of the food can affect various life history traits of Daphnia. More specifically, the effect of the elemental composition of algae, expressed as the C:P ratio, has been studied intensively. Daphnia species differ in their response to differences in the C:P ratio of their food. Until now, it has been unclear whether these species differences are driven by phylogenetic constraints or by adaptation to particular environmental conditions. Here we present laboratory experiments with 12 Daphnia species from three different subgenera originating from a broad range of habitats. We compared somatic growth rates and sensitivity to variation in the nutrient stoichiometry of the food with habitat parameters, taking into account the phylogenetic history of the species. No associations between fitness and habitat parameters were detected. However, we found a trade-off between sensitivity to P-deficient diets and the maximum growth rate on a P-sufficient diet. In several cases, this trade-off helps to explain the association between species distribution and habitat parameters. We observed no correlation of the sensitivity to P limitation with the phylogenetic history of the genus Daphnia. Thus, we conclude that the differential responses among Daphnia species to variation in P content in food were driven mainly by adaptations to their local habitats, and are not constrained by deep evolutionary patterns.

The genetic and environmental basis of adaptive differences in shoaling behaviour among populations of Trinidadian guppies, Poecilia reticulata

The degree of plasticity an individual expresses when moving into a new environment is likely to influence the probability of colonization and potential for subsequent evolution. Yet few empirical examples exist where the ancestral and derived conditions suggest a role for plasticity in adaptive genetic divergence of populations. Here we explore the genetic and plastic components of shoaling behaviour in two pairs of populations of Poecilia reticulata (Trinidadian guppies). We contrast shoaling behaviour of guppies derived from high- and low-predation populations from two separate drainages by measuring the shoaling response of second generation laboratory-reared individuals in the presence and absence of predator induced alarm pheromones. We find persistent differences in mean shoaling cohesion that suggest a genetic basis; when measured under the same conditions high-predation guppies form more cohesive shoals than low-predation guppies. Both high and low-predation guppies also exhibit plasticity in the response to alarm pheromones, by forming tighter, more cohesive shoals. These patterns suggest a conserved capacity for adaptive behavioural plasticity when moving between variable predation communities that are consistent with models of genetic accommodation.

Habitat Selection of a Large Herbivore at High Density and Without Predation: Trade-off between Forage and Cover?

selection under harsh environmental conditions. We fitted 19 female white-tailed deer with global positioning system collars and delineated summer home ranges and core areas. We sampled vegetation in the core areas and in the rest of the home ranges to determine abundance of forage and forest cover within habitat patches, and assessed habitat selection between open and forested habitat patches. At a coarse scale, white-tailed deer preferred open habitat patches over forested ones, suggesting that they adopted a foraging strategy favoring energy intake. At a fine scale, habitat selection was influenced positively by the percentage of ground cover of forbs and deciduous shrubs, but negatively by conifer density. The biomass of preferred plant species, lateral cover, fir regeneration, and distance to the nearest open–forest edge were not strong predictors of habitat selection by deer. We conclude that fine-scale habitat selection by white-tailed deer at high population density and in the absence of predation is mainly determined by forage abundance. These patterns of habitat selection demonstrate that herbivores can adjust their behavior to other limiting factors when predation risk is relaxed.

Testing the effects of resource distribution and inherent habitat riskiness on simultaneous habitat selection by predators and prey

Theoretical models have extended the Ideal Free Distribution model to examine predator–prey systems having three trophic levels, when both predator and prey are allowed to move freely. One consistent prediction made by such models is that the spatial distribution of prey should be mainly determined by the inherent habitat riskiness (e.g. cover level), with prey avoiding the inherently riskier habitats regardless (or nearly so) of resource distribution. To test this prediction, we conducted laboratory experiments in which both predators (creek chub, Semotilus atromaculatus) and prey (northern redbelly dace, Phoxinus eos) were free to move between feeding patches differing in resource quantity and habitat riskiness. When alone, creek chub and northern redbelly dace both preferred the more food-rich patch. The spatial distribution of dace was also inversely related to that of creek chub in the presence of chub fenced into feeding patches. When the patches differed in both riskiness and resource quantity, the spatial distribution of dace was mainly influenced by resource distribution and, to a lesser extent, by the inherent habitat riskiness in the absence of predators. In the presence of creek chub, the dace significantly decreased their use of the inherently riskier patch compared to when predators were absent. However, contrary to the models' prediction, food distribution still significantly influenced dace distribution when predators were present. Finally, dace aggregated increasingly in a third, totally safe area (but one offering no food) as the number of chub present in both patches increased. Thus, the influence of resource distribution and inherent habitat riskiness on prey distribution seems to vary with the level of predation risk.

Testing for the relative contribution of patch neighborhood, patch internal structure, and presence of predators and competitor species in determining distribution patterns of rodents in a fragmented landscape

Factors affecting the distribution of species in fragmented landscapes, and their relative importance, are often unclear. Few studies have deliberately compared various hypotheses in relatively controlled conditions. Moreover, most studies to date have not incorporated false absences in their modeling. Following a multiple hypotheses testing framework, we tested the relative role of landscape structure, patch and neighborhood configuration, patch internal structure, presence or absence of predators, and presence or absence and abundance of potential competitor species on the occupancy patterns of three rodent species ( Myodes glareolus (Schreber, 1780), Apodemus flavicollis (Melchior, 1834), Apodemus sylvaticus (L., 1758)) in a highly fragmented landscape in Tuscany, central Italy. Distribution patterns and occupancy dynamics of the three rodent species were affected by patch and patch neighborhood characteristics, as well as the vicinity of other patches occupied by the species. However, we found no relevant effect of the surrounding landscape structure, patch internal structure, predator patch use, and abundance or distribution of potential competitor species. The observed spatial correlation between populations and the evidence of colonization or extinction events suggest that a metapopulation approach could provide a good framework for understanding the long-term dynamics of these populations.

Ecological restoration in New Zealand – current trends and future challenges

Ecological restoration in New Zealand – current trends and future challenges

Non-volant small mammal community responses to fragmentation of kerangas forests in Brunei Darussalam

This paper summarises the effects of kerangas forest fragmentation on the non-volant small mammal community resident in the fragments based on a long term study conducted in Brunei Darussalam. These effects are shown as eight responses—a significant reduction in the species richness and diversity in relation to size of fragments, the disappearance of species with large home ranges and specific habitat requirements, invasion of generalists/opportunists into the fragments from degraded habitats, absence of predators, a possible reduction in the activity space of generalists in fragments, erosion in the trophic structure of the small mammal community, changes in the small mammal abundance in relation to fragment size and dominance of one species over other co-occurring species in an isolated fragment. These responses are briefly explained and their significance discussed.

Bone growth marks reveal protracted growth in New Zealand kiwi (Aves, Apterygidae)

The presence of bone growth marks reflecting annual rhythms in the cortical bone of non-avian tetrapods is now established as a general phenomenon. In contrast, ornithurines (the theropod group including modern birds and their closest relatives) usually grow rapidly in less than a year, such that no annual rhythms are expressed in bone cortices, except scarce growth marks restricted to the outer cortical layer. So far, cyclical growth in modern birds has been restricted to the Eocene Diatryma, the extant parrot Amazona amazonica and the extinct New Zealand (NZ) moa (Dinornithidae). Here we show the presence of lines of arrested growth in the long bones of the living NZ kiwi (Apteryx spp., Apterygidae). Kiwis take 5-6 years to reach full adult body size, which indicates a delayed maturity and a slow reproductive cycle. Protracted growth probably evolved convergently in moa and kiwi sometime since the Middle Miocene, owing to the severe climatic cooling in the southwest Pacific and the absence of mammalian predators.

Variation along the shy–bold continuum in extremophile fishes (Poecilia mexicana, Poecilia sulphuraria)

One potential trade-off that bold individuals face is between increased predation risks and gains in resources. Individuals experiencing high predation and hungry individuals (or individuals with low body condition) are predicted to show increased boldness. We examined one behavioral trait previously reported to be associated with boldness (the time individual fish needed to emerge from shelter) in various populations of mollies (Poecilia spp.). Our study system included several southern Mexican surface streams with high piscine predation and high food availability, sulfidic surface streams with high avian predation, in which the inhabiting fish show reduced body condition, and a sulfidic cave, where predation and body condition are low. Our comparison revealed very short times to emerge from the start box in populations from non-sulfidic streams. In sulfidic habitats (whether surface or cave), it took individual Poecilia mexicana considerably longer to emerge from the start box, and the same difference was also found in an independent comparison between P. mexicana and the closely related, highly sulfide-adapted Poecilia sulphuraria. Fish reared under common garden conditions (in the absence of predators and hydrogen sulfide) showed intermediate boldness scores to the extremes observed in the field. Our data thus indicate that (a) boldness is shaped by environmental conditions/experiential effects, but is not heritable, (b) predation affects boldness in the predicted direction, but (c) low body condition leads to reduced boldness. Extremophile Poecilia spp. spend most of their time surfacing to survive under sulfidic and hypoxic conditions, which exposes them to increased levels of predations, but the fish forage on the bottom. Hence, in this system, increased boldness does not increase foraging success. We argue that energy limitation favors reducing energetically costly behaviors, and exploring novel environments may be just one of them.

Predatory Potential of <I>Geocoris</I> spp. and <I>Orius insidiosus</I> on Fall Armyworm in Resistant and Susceptible Turf

Predatory potential and performance of the predaceous heteropterans, Geocoris punctipes (Say), G. uliginosus (Say) (Geocoridae), and Orius insidiosus (Say) (Anthocoridae), were evaluated using fall armyworm, Spodoptera frugiperda (J. E. Smith), as prey on different turfgrass taxa (resistant zoysiagrasses, 'Cavalier' and 'Palisades'; moderately resistant Bermuda grass, 'TifSport'; and susceptible seashore paspalum, 'Sea Isle 1') through laboratory and field studies. When background mortality was taken into account, in small arena trials in the laboratory, the greatest mortality by predators occurred on TifSport. The predator impact on TifSport by O. insidiosus was 92.6% above the mortality in the no-predator treatment on that grass. Predator induced mortality was rarely significant on the highly resistant zoysiagrass cultivar Cavalier because mortality, even in the absence of predators, was so high. Survival of larvae on TifSport Bermuda grass was significantly reduced by the addition of just two O. insidiosus per pot in laboratory pot trials. An increase in predator density to 4, 6, 8, or 10 further suppressed larval survival. O. insidiosus reduced larval survival on Sea Isle 1 at all densities. On Sea Isle 1, a density of two O. insidiosus resulted in > 50% reduction in live fall armyworms compared with the no predator treatment in laboratory trials. However, addition of O. insidiosus did not significantly reduce survival of fall armyworm larvae on this cultivar in the field in the presence of alternative prey and predators. O. insidiosus densities of six or higher per 181.4 cm2 did significantly reduce larval survival on TifSport Bermuda grass by as much as 80% during a 5-d trial period in the field. Predator-induced mortality among all trials was most consistent on a grass of intermediate resistance, TifSport Bermuda grass.

Predators indirectly control vector-borne disease: linking predator–prey and host–pathogen models

Pathogens transmitted by arthropod vectors are common in human populations, agricultural systems and natural communities. Transmission of these vector-borne pathogens depends on the population dynamics of the vector species as well as its interactions with other species within the community. In particular, predation may be sufficient to control pathogen prevalence indirectly via the vector. To examine the indirect effect of predators on vectored-pathogen dynamics, we developed a theoretical model that integrates predator-prey and host-pathogen theory. We used this model to determine whether predation can prevent pathogen persistence or alter the stability of host-pathogen dynamics. We found that, in the absence of predation, pathogen prevalence in the host increases with vector fecundity, whereas predation on the vector causes pathogen prevalence to decline, or even become extinct, with increasing vector fecundity. We also found that predation on a vector may drastically slow the initial spread of a pathogen. The predator can increase host abundance indirectly by reducing or eliminating infection in the host population. These results highlight the importance of studying interactions that, within the greater community, may alter our predictions when studying disease dynamics. From an applied perspective, these results also suggest situations where an introduced predator or the natural enemies of a vector may slow the rate of spread of an emerging vector-borne pathogen.

Functional response in habitat selection and the tradeoffs between foraging niche components in a large herbivore

How herbivore behaviour is influenced by changes in resource levels is central for understanding trophic interactions. We examined whether foraging tradeoffs change with food levels by comparing habitat selection and space use within and between two neighbouring, predator‐free Svalbard reindeer populations. The populations faced different food levels due to contrasting grazing history. Summer resource selection in radiocollared females was assessed by a multi‐dimensional niche approach based on habitat variables obtained from a satellite image (e.g. the normalised difference vegetation index, NDVI) and a digital terrain model. The population at the overgrazed Brøggerhalvøya faced overall lower plant cover, biomass and primary productivity (i.e. lower NDVI) than the population at Sarsøyra. At Brøggerhalvøya, most reindeer selected for productive habitat when choosing home range and patches within the home range. In contrast, habitat selection at Sarsøyra was more affected by abiotic conditions such as moisture, which may influence plant quality. Here, reindeer used patches with even less biomass than the average reindeer at the poorer Brøggerhalvøya. Such a difference in habitat preference with different habitat availability (a functional response in habitat selection) probably reflected increased selection for high‐quality forage at the expense of high forage quantity at Sarsøyra. Accordingly, a negative relationship between habitat productivity and home range size was only present across individuals within Brøggerhalvøya, where forage quantity was the important foraging niche component. Individuals having poor (and large) home ranges apparently could not compensate for this by higher patch selectivity compared to individuals with richer home ranges. The results indicate changes in foraging tradeoffs at contrasting resource levels and that strong interactions occur between habitat selection, space use and the foraging niche structure in the absence of predation.

Patterns of reproduction in Malayan silvered leaf monkeys at the Bronx Zoo

Within phylogenetic limits reproductive characteristics of a given species may vary between populations in response to ecological and social factors. For instance, in environments where high quality nutrition is readily available, the onset and speed of reproduction are often accelerated. Other influencing factors might be maternal experience or the sex of the infant. Here we present data on reproductive characteristics for the silvered leaf monkey (Trachypithecus cristatus), a medium-sized Asian colobine housed at the Wildlife Conservation Society's Bronx Zoo as a one-male group. To place the species into an appropriate phylogenetic context, we limited our comparison to other colobine species. Demographic data span 21.4 years (October 1985 to March 2007) and derive from 30 adult females (128.0 female years). Detailed behavioral data stem from a 2.2 years study (November 2002 to January 2005; 734 days, 4,225 hr). As in other Asian colobines, receptive periods were short (mean=4.3 days, n=68). This is expected for one-male groups where receptivity likely indicates, rather than conceals, ovulation. Gestation length was estimated based on a change in the pattern of sexual behavior (mean=194.6 days, n=7). It fell within the range reported for the taxon. Births occurred year round, at an early age (mean=2.9 years, n=8), at short intervals (mean=14.9 months, n=59) in combination with a short lactation (mean 12.1 months, n=9) likely due to the nearly unlimited availability of nutrition in this zoo setting. Primiparous females tended to have a longer first interbirth interval but infant survival rates were similar to multipara possibly due to the absence of predators. Maternal investment was independent of the infant's sex and birth sex ratio was even. Our results emphasize that when interpreted with caution, zoo populations yield realistic reproductive characteristics that can help fill the gap in our knowledge about colobine life history.

What do caprellids (Crustacea: Amphipoda) feed on?

The present study represents the first comprehensive work dealing with the dietary analysis of Caprellidea. We studied 743 specimens of 31 genera and 62 species from all around the world. Analysis of digestive contents revealed that caprellids are mainly detritivores (detritus represented the 86% of the caprellid diet), but a small percentage of species, those lacking molars belonging to the Phtisicinae, can be considered as obligate predators and feed mainly on small crustaceans (copepods and other amphipods) and polychaetes. The contribution of sponges, hydroids, macroalgae, diatoms and dinoflagellates to the caprellid diet was very low (<2%). Apart from the clear relationship between the absence of molar process and predators, no other correlations between digestive contents and mouthpart structure were found. Cluster analysis based on the dietary data indicated a patent segregation between the Phtisicinae (obligate predators) and Caprellinae (detritivores, detritivores/predators or opportunistics) and could support the hypothesis of basal divergence in two major lines of evolution: Phtisicinae and Caprogammaridae–Caprellinae. Consequently, the debate questioning if the taxon Caprellidea is a monophyletic group or not is still open. Additional morphological, molecular and behavioral studies are necessary to define the evolutionary relationships in this group of crustaceans.

Reply to the Comment on “The ‘living-fossil’ community of the cyrtocrinid Cyathidium foresti and the deep-sea oyster Neopycnodonte zibrowii (Azores Archipelago)” by M. Wisshak, C. Neumann, J. Jakobsen and A. Freiwald [Palaeogeography, Palaeoclimatology, Palaeoecology 271 (2009) 77–83

We underline the criticism expressed in Wisshak et al., 2009 (“The ‘living-fossil’ community of the cyrtocrinid Cyathidium foresti and the deep-sea oyster Neopycnodonte zibrowii (Azores Archipelago)” Palaeogeography, Palaeoclimatology, Palaeoecology 271, 77–83: p. 81) on the speculation by Donovan and Jakobsen, 2004 (An unusual crinoid barnacle association in the type area of the Danian (Paleocene, Denmark). Lethaia 37: 407–415: p. 413) that cyrtocrinids and barnacles may have thrived together as pseudoplankton on driftwood. Even though this hypothesis is conceivable, it remains unlikely. The data basis is neither sufficient to conclude with confidence that suitable habitat was unavailable close at hand, nor to exclude that the sediment accumulation in question had undergone considerable transport, nor is there any direct or indirect evidence for a wooden substrate. Although it cannot be ruled out altogether that some Cyathidium holopus individuals may have attached themselves to floating logs, thereby benefiting from the absence of benthic predators, the overwhelming majority of the Danian cyrtocrinids settled on the seafloor and reflect the overall habitat shift of these crinoids towards deeper waters by the Early Cenozoic.

Experimental displacement trials of the red sea urchin Strongylocentrotus franciscanus (Aggassiz, 1863) (Echinodermata: Echinoidea) at different current velocities

Displacement of marine animals is affected by diverse environmental factors, including hydrodynamics performance. We evaluated the effect of current velocity on the displacement of the sea urchin Strongylocentrotus franciscanus in an experimental flume, in both light and dark conditions. We observed that movement of S. franciscanus was directly proportional to the current speed. Our results differ from previous studies in the amount and the direction of displacement of other strongylocentrotids, because sea urchins displacements were similar in the current direction and countercurrent irrespective of current velocity and our results showed displacements of circa 7 m per day, smaller to that reported for experiments in the same urchin species in British Columbia. The differences may be due to the absence of predators or food, or the trials in day and night conditions. Day and night differences in the displacement of S. franciscanus were not observed.

Predicting population survival under future climate change: density dependence, drought and extraction in an insular bighorn sheep

1. Our understanding of the interplay between density dependence, climatic perturbations, and conservation practices on the dynamics of small populations is still limited. This can result in uninformed strategies that put endangered populations at risk. Moreover, the data available for a large number of populations in such circumstances are sparse and mined with missing data. Under the current climate change scenarios, it is essential to develop appropriate inferential methods that can make use of such data sets. 2. We studied a population of desert bighorn sheep introduced to Tiburon Island, Mexico in 1975 and subjected to irregular extractions for the last 10 years. The unique attributes of this population are absence of predation and disease, thereby permitting us to explore the combined effect of density dependence, environmental variability and extraction in a 'controlled setting.' Using a combination of nonlinear discrete models with long-term field data, we constructed three basic Bayesian state space models with increasing density dependence (DD), and the same three models with the addition of summer drought effects. 3. We subsequently used Monte Carlo simulations to evaluate the combined effect of drought, DD, and increasing extractions on the probability of population survival under two climate change scenarios (based on the Intergovernmental Panel on Climate Change predictions): (i) increase in drought variability; and (ii) increase in mean drought severity. 4. The population grew from 16 individuals introduced in 1975 to close to 700 by 1993. Our results show that the population's growth was dominated by DD, with drought having a secondary but still relevant effect on its dynamics. 5. Our predictions suggest that under climate change scenario (i), extraction dominates the fate of the population, while for scenario (ii), an increase in mean drought affects the population's probability of survival in an equivalent magnitude as extractions. Thus, for the long-term survival of the population, our results stress that a more variable environment is less threatening than one in which the mean conditions become harsher. Current climate change scenarios and their underlying uncertainty make studies such as this one crucial for understanding the dynamics of ungulate populations and their conservation.

Vulnerability of ground-nesting waterbirds to predation by invasive American mink in the Cape Horn Biosphere Reserve, Chile

Biological invasions constitute one of the most important threats to biodiversity. This is especially true for “naïve” birds that have evolved in the absence of terrestrial predators in island ecosystems. The American mink ( Mustela vison) has recently established a feral population on Navarino Island (55°S), southern Chile, where it represents a new guild of terrestrial mammal predators. We investigated the impact of mink on ground-nesting coastal waterbirds with the aim of deriving a vulnerability profile for birds as a function of different breeding strategies, habitat, and nest characteristics. We compared rates of nest survival and mink predation on 102 nests of solitary nesting species ( Chloephaga picta, Tachyeres pteneres), on 361 nests of colonial birds ( Larus dominicanus, Larus scoresbii, Sterna hirundinacea), and on 558 artificial nests. We calculated relative mink and bird densities at all nest sites. Nests of colonial species showed the highest nest survival probabilities (67–84%) and no predation by mink. Nest survival rates for solitary nesting species were lower (5–20%) and mink predation rates higher (10–44%). Discriminant analyses revealed that mink preyed upon artificial nests mainly at shores with rocky outcroppings where mink were abundant. High nest concealment increased the probability for predation by mink. Conservation planning should consider that invasive mink might severely affect the reproduction success of bird species with the following characteristics: solitary nesting, nesting habitat at rocky outcrop shores, and concealed nests. We recommend that work starts immediately to control the mink population with a priority in the nesting habitats of vulnerable endemic waterbirds.

Diseases of the Red-Legged Partridge (Alectoris rufa L.): a review

In spite of the ecological and socio-economical importance of the red-legged partridge (Alectoris rufa) as a prey of threatened species and as a gamebird, and the reported influence that pathogens have in other populations of galliform birds, information about diseases of the red-legged partridge is still scarce. Very little is known about the importance of the diseases in the dynamics of free-living partridge populations. However, enzootic avian poxvirus may be causing the death of partridge chicks in some natural populations. In contrast, more evidences support that the intense management of partridges (trough release of farm-reared partridges, supplemental feeding, or predator control) are promoting the release and transmission of infectious and parasitic diseases. Infectious and protozoan agents and monoxenous helminths typical from farmed galliforms (Ascaridia sp., Eucoleus contortus, or Heterakis gallinarum) are extremely frequent in partridge rearing facilities. The presence of such helminths but also other disease outbreaks (e.g. salmonellosis) in wild partridges may be related with the release of farm-reared partridges. Other cases of disease in the wild, such as avian tuberculosis, may be favoured by the aggregation of partridges and other birds around feeders and water points, and by the absence of predators that should remove sick partridges. Intense supplementary feeding may also promote patho-physiological troubles, such as an incorrect development and eventual massive deaths of juvenile wild partridges in summer months. These and other available reports of infectious and parasitic agents and other diseases of diverse aetiology are reviewed.