Prevalence of nest predators in a sub-Arctic ecosystem

High nest loss is an important driver of gallinaceous bird population dynamics. Identifying factors determining the spatial distribution of potential nest predators and thereby indirectly risk of nest losses is therefore essential. The aim of this 1-year study was to estimate relative predation rates on artificial ground nests in willow ptarmigan (Lagopus lagopus) habitats, along replicate altitudinal gradients (transects, n?=?60) spanning from sub-Arctic birch forest to the low-alpine tundra in three locations in northern Norway. In each transect, one artificial nest (track board) was placed in three different habitats: (1) birch forest, (2) edge between birch forest and low-alpine tundra and (3) low-alpine tundra. Total predation rates over all habitats within locations ranged from 47.4% to 77.5% and did not vary systematically in space and time. The average predation rate by avian predators was consistently high (58%), and mammalian predation rate was consistently low (5.6%). The consistently high level of predation inflicted by birds was mainly due to omnipresent corvids, especially the hooded crow (Corvus cornix). Analysis of species-specific predation rates showed that habitat and location effects were insignificant for all species, except for raven (Corvus corax) that showed clearly higher predation in one of the locations. The results indicate that from the perspective of the spatial distribution of potential nest predators in sub-Arctic birch forest, ground nesting birds like willow ptarmigan should not be expected to be selective with respect to nesting habitat in the ecotone between birch forest and the low-alpine tundra.     

Predator presence may benefit: kestrels protect curlew nests against nest predators

We studied whether the presence of breeding kestrels (Falco tinnunculus) affected nest predation and breeding habitat selection of curlews (Numenius arquata) on an open flat farmland area in western Finland. We searched for nests of curlews from an area of 6 km² during 1985–1993. For each nest found, we recorded the fate of the nest, and the distance to the nearest kestrel nest and to the nearest perch. We measured the impact of breeding kestrels on nest predation by constructing artificial curlew nests in the vicinity of ten kestrel nests in 1993. Curlew nests were closer to kestrel nests than expected from random distribution, eventhough kestrels fed on average 5.5% of curlew chick production. Predation risk by kestrels was lower than predation risk by corvids and other generalist predators, which predated 9% of curlew nests surviving farming practices and an unknown proportion of chicks. Artificial nest experiment showed that nest predation was lower close to kestrel nests than further away suggesting that the breeding association of curlews and kestrels was a behavioural adaptation against nest predation. Thus, the presence of a predator may sometimes be beneficial to prey, and prey animals have behavioural adaptations to these situations.     

Foraging behaviour of nest predators at open-cup nests of woodland passerines

Nest predation patterns and processes cannot be understood without studying the behaviour of predators. I videotaped the behaviour of 22 species of predators at 171 depredated nests of 13 passerine species, in woodland in the Czech Republic. About 32% (60/187) of all events occurred during the night; mammals accounted for 95% (57/60) and 22% (28/127) of nocturnal and diurnal predation, respectively. About 67% (57/85) of mammalian predation, but only 3% (3/102) of avian predation, occurred during night. Multiple predations by the same species were detected in at least 7% (6/82) and 42% (37/88) of nests depredated by mammals and birds, respectively. Martens Martes martes/foina took nest content mostly all at once; birds (mainly Jay Garrulus glandarius) revisited partially depredated nest during 1–4 consecutive days. Martens stayed at the depredated nest about five times longer than Jays. Martens spent similar time at nests with eggs and nestling, while Jays stayed about twice longer at nests with eggs. Mammals consumed eggs always at the nest (23/23), but took nestlings away in at least 48% (31/64) cases. Birds took the eggs and nestling away in at least 31% (18/58) and 76% (71/94) cases, respectively. Predator visits to active nests without taking the content, repeated partial predation and revisitation of previously depredated nests suggest an effect of memory on predator’s foraging behaviour.     

Increased parental care cost for nest-guarding fish in a lake with hyperabundant nest predators

Although parental care increases offspring survival, providingcare is costly, reducing parental growth and survival and, thereby,compromising future reproductive success. To determine if anexotic benthic predator might be affecting parental care bynest-guarding smallmouth bass (Micropterus dolomieu), we comparednest-guarding behavior and energy expenditures in two systems,one with a hyperabundant recently introduced predator, the roundgoby (Neogobious melanostomus). In Lake Erie, USA, smallmouthbass vigorously defended their nests from benthic round gobies.In Lake Opeongo, Canada, smallmouth bass were exposed to fewerand predominantly open-water predators and were less activein their nest defense. From scuba and video observations, wedocumented that nest-guarding smallmouth bass chased predators(99% of which were round gobies) nine times more frequentlyin Lake Erie than in Lake Opeongo. This heightened activityresulted in a significant decline in weight and energetic contentof guarding males in Lake Erie but no change in Lake Opeongomales. Bioenergetic simulations revealed that parental careincreased smallmouth bass standard metabolic rate by 210% inLake Erie but only by 28% in Lake Opeongo. As energy reservesdeclined and offspring became increasingly independent, malesin both lakes consumed more prey and spent more time foragingaway from their nests; however, nest-guarding smallmouth bassconsumed few prey and, in Lake Erie, rarely consumed round gobies.Therefore, increased parental care costs owing to the presenceof round gobies could affect future growth, reproduction, andsurvival if smallmouth bass approach critically low energy reserves.     

Artificial nest predation and habitat fragmentation: different trends in bird and mammal predators

Predation on artificial nests was studied in Belgian deciduous forest fragments between 1 and 200 ha Predation rates were compared to fragment size, distance from the forest edge, time period (three replicates), and nest type (ground and tree) Logistic regression analysis showed that overall nest predation did not vary with distance from the edge, forest size, and time period Birds represented over 70% of all predator attacks but their importance decreased in larger areas and away from the forest edge where mammals were responsible for much of the nest predation It is concluded that the effect of habitat fragmentation depends on the composition of the local predator community     

Eastern bluebirds Sialia sialis do not avoid nest boxes with chemical cues from two common nest predators

Chemodetection of common nest predators may be advantageous for nesting birds; however, few studies have examined the ability of songbirds to detect chemical odors from predators. Thus, in 2002, we presented eastern bluebirds Sialia sialis with pairs of nest boxes; one box in the pair was regularly scented with chemical cues from a common nest predator, the black rat snake Elaphe obsoleta , and the other with a neutral cue. In 2004, we again presented bluebirds with pairs of boxes, one scented with chemical cues from a different nest predator, the deer mouse Peromyscus maniculatus , and the other with a neutral scent. Although human females were able to correctly distinguish paper laced with predator cues from paper with neutral cues, bluebirds were as likely to lay eggs in boxes with predator cues as in boxes with neutral cues. While it remains possible that bluebirds may detect scent from potential nest predators, it appears that the presence of these chemical cues does not ultimately influence selection of nest sites.     

The efficiency of a new lightweight suction sampler for sampling aphids and their predators in arable land

A petrol driven machine, normally used to collect leaf litter, was modified to be used as a suction sampler for polyphagous predators in cereals and grassy habitats and aphids in cereals. Recovery efficiency of Araneae, Carabidae and Staphylinidae did not differ significantly between winter sampling from Agrostis stolonifera, Dactylis glomerata, Festuca rubra, Holcus lanatus or Lolium perenne although the structure of these grasses was very different. Summer sampling of aphids and their predators in winter wheat showed that the new sampler captured significantly more target organisms per unit area than did a traditional suction sampler. The machine was also lighter, cheaper and much easier to use than a traditional machine.     

Density-dependent nest predation in waterfowl: the relative importance of nest density versus nest dispersion

When nest predation levels are very high or very low, the absolute range of observable nest success is constrained (a floor/ceiling effect), and it may be more difficult to detect density-dependent nest predation. Density-dependent nest predation may be more detectable in years with moderate predation rates, simply because there can be a greater absolute difference in nest success between sites. To test this, we replicated a predation experiment 10 years after the original study, using both natural and artificial nests, comparing a year when overall rates of nest predation were high (2000) to a year with moderate nest predation (2010). We found no evidence for density-dependent predation on artificial nests in either year, indicating that nest predation is not density-dependent at the spatial scale of our experimental replicates (1-ha patches). Using nearest-neighbor distances as a measure of nest dispersion, we also found little evidence for "dispersion-dependent" predation on artificial nests. However, when we tested for dispersion-dependent predation using natural nests, we found that nest survival increased with shorter nearest-neighbor distances, and that neighboring nests were more likely to share the same nest fate than non-adjacent nests. Thus, at small spatial scales, density-dependence appears to operate in the opposite direction as predicted: closer nearest neighbors are more likely to be successful. We suggest that local nest dispersion, rather than larger-scale measures of nest density per se, may play a more important role in density-dependent nest predation.     

A predator's perspective of nest predation: predation by red squirrels is learned,not incidental

Nest predation has been used to explain aspects of avian ecology ranging from nest site selection to population declines. Many arguments rely on specific assumptions regarding how predators find nests, yet these predatory mechanisms remain largely untested. Here we combine artificial nest experiments with behavioural observations of individual red squirrels Tamiasciurus hudsonicus to differentiate between two common hypotheses: predation is incidental versus learned. Specifically, we tested: 1) whether nest survival could be explained solely by a squirrel's activity patterns or habitat use, as predicted if predation was incidental; or 2) if predation increased as a squirrel gained experience preying on a nest, as predicted if predation was learned. We also monitored squirrel activity after predation to test for evidence of two search mechanisms: area‐restricted searching and use of microhabitat search images. Contrary to incidental predation and in support of learning, squirrels did not find nests faster in areas with high use (e.g. forest edges). Instead, survival of artificial nests was strongly related to a squirrel's prior experience preying on artificial nests. Experience reduced nest survival times by over half and increased predation rates by 150–200%. Squirrels returned to and doubled their activity at the site of a previously preyed on nest. However, neither area‐restricted searching nor microhabitat search images can explain how squirrels located artificial nests more readily with experience. Instead, squirrels likely used cues associated with the nests or eggs themselves. Learning implies that squirrels could be increasingly effective predators as the density or profitability of nests increases. Our results add support to the view that nest predation is complex and broadly influenced (e.g. by predator experience, motivation), and is unlikely to be predicted consistently by simple relationships with predator activity, abundance or habitat.     

Identification and functional perspective of a novel HLA-A allele: A*0279

A novel HLA-A allele, HLA-A*0279, was identified using PCR-SSP and PCR-SBT methods. It is inheritable. HLA-A*0279 differs from HLA-A*020601 by a single nucleotide at position 497 in exon 3, leading to an amino acid change from Threonine to Isoleucine at the alpha2 helix of HLA molecule. To investigate whether the altered amino acid residue could affect its peptide-binding repertoire, we compared the predicted crystal structure of HLA-A*020601 and HLA-A*0279 by Swiss-PdbViewer software analysis. We found that the crystal structure of the two molecules is very similar except for a difference in the number of hydrogen bonds they can possibly form, which in turn could affect their structural stability. To test whether HLA-A*0279 has the ability to cross-present A*0201 - restricted peptides to T cells, the full lenght cDNA of HLA-A*0201, -A* 020601 and -A*0279 were respectively transfected into COS-7 cells, which were then used as targets in IFN-gamma release Elispot assay. A*2079 was found to be able to present A*0201- restricted peptides to and induce the response of CTL, thus it can be classified as member of the HLA-A2 functional supertype family. This finding would benefit the design of peptide vaccines to be applied in broader populations.The nucleotide sequence data reported in this paper have been submitted to the Genbank nucleotide sequence database and have been assigned the accession numbers AY856830 and HWS10002813.The name HLA-A*0279 was officially assigned by the World Health Organization Nomenclature Committee in January 2005.     

To nest communally or not to nest communally: a review of rodent communal nesting and nursing

Communal nesting, the sharing of parental responsibilities between multiple individuals in a nest, is common in many rodents. Upon first glance, this behaviour seems to be selectively disadvantageous. Communal care not only involves energetic costs, but may also be subject to cheating behaviour. Despite abundant literature, many questions remain regarding advantages gained by females that form nesting groups. I discuss the communal nesting of eusocial, singular and plural breeding rodents. I first clarify the distinction between communal nesting and thermoregulatory huddling. I then review two major groups of hypotheses ('ecological constraints' and 'benefits of philopatry') that are used to explain the occurrence of communal nesting in rodents. Most likely, these hypotheses are not mutually exclusive. Regardless of the main selective pressure(s) acting on communal nesting, the indirect components of inclusive fitness that result from nest sharing most likely influence the formation and maintenance of communal nests. Communal nesting and nursing (the sharing of milk with nonoffspring) are under different selective regimes and thus, must be evaluated separately. I review adaptive and nonadaptive hypotheses for rodent communal nursing. I argue that communal nursing may not be adaptive as mothers may be forced to share milk with nonoffspring in large communal nests (i.e. communal nursing may be a cost associated with communal nesting). In conclusion, I propose directions for future study that may improve our understanding of communal nesting and nursing in the wild. Copyright 2000 The Association for the Study of Animal Behaviour.     

An alternative strategy for maintenance of eusociality after nest destruction: new nest construction in a primitively eusocial wasp

Although nests are central to colonial life in social insects, nests are sometimes damaged by predators or natural disasters. After nest destruction, individuals usually construct new nests. In this case, a sophisticated mechanism like the scent trail pheromone used in large insect colonies that recruit individuals to new nest sites would be important for the maintenance of eusociality. In independent-founding Polistes wasps, it is well known that queens enforce workers physiologically on the natal nests even if evidence of trail pheromone use has not been exhibited. We investigated the effect of the queen on an alternative strategy for the maintenance of eusociality by first females after nest destruction in the primitively eusocial wasp Polistes chinensis. We predicted that the first females in queen-absent colonies have various behavioral options after nest destruction. Even if the females construct new nests cooperatively with other individuals, the new nest construction should be conducted more smoothly in queen-present colonies because the queens regulate the behavior of wasps. We made wasps construct new nests by removing the entire brood from existing nests. The presence of the queen did not cause variation in the alternative strategy of the first females, as the first females (workers) usually constructed new nests cooperatively irrespective of the queen-presence. Thus, the workers in the queenpresent colonies affiliated to the new nest construction more smoothly and constructed new nests more efficiently than workers in the queen-absent colonies. Our results suggest that the presence of the queen is important for maintaining eusociality in primitively eusocial wasps after nest destruction. Received 8 February 2005; revised 5 October 2005; accepted 17 October 2005.     

Temporally fluctuating prey and interfering predators: a positive feedback

Prey densities often show fluctuating patterns over various timescales. Focusing on short-term, within-generation fluctuating patterns of local prey availability, we suggest that prey that show synchronized and high-amplitude fluctuations in availability experience decreased risks of predation, but also enhance the maintenance of predator interference hierarchies by affecting the relative foraging success of unequal conspecific interferers. When predators interfere with each other, they forage less intensely on prey, which benefits prey in terms of decreased predation risk. The system hence involves a positive feedback. We thus argue that short-term temporal fluctuations in local prey availability could be an important mechanism behind how interference-structured social predator systems are developed and sustained. The temporal fluctuations also have implications for the phenotypic diversity of predators, and may be involved in speciation processes.     

Hepatoimmunology: a perspective

Premises for the subspecialty of hepatoimmunology include the recognition that the liver is a lymphoid organ with unique immunological properties. These properties ensure efficient innate defence against intestinal microbes and toxins, confer a particular capacity for induction of tolerance, and provide for apoptotic disposal of redundant lymphocytes. Pathological responses within the liver are elicited when: (i) hepatotropic viruses (hepatitis virus B and C) escape immune elimination and reside in hepatocytes; (ii) the liver becomes the site of autoimmune responses directed against either hepatocytes (autoimmune hepatitis) or biliary ductules (primary biliary cirrhosis); or (iii) the liver in the course of disposal of drugs generates neoantigens that provoke adverse allergic responses. Recent advances in the understanding of the immunopathogenesis of these entities are reviewed.     

Individual scent marking of the nest entrance as a mechanism for nest recognition inXylocopa pubescens (Hymenoptera: Anthophoridae)

The mechanism by which female Xylocopa pubescenslocate their nest in a nesting aggregation was investigated. The bees were induced to nest in canes to which uniform nest entrances were attached. The results of nest displacement experiments revealed that the bees use visual cues for proximate orientation,but at very close range they also use olfactory cues. This conclusion was corroborated by the results of experiments in which the nest entrances were either removed or exchanged for alien nest entrances. Moreover, habituation experiments strongly indicated that the bees impart their individual marking at the nest entrance and that they can learn and memorize the individual odors of the neighboring bees.     

Active foragers vs. sit-and-wait predators: a simple model

I propose a simple model for the decision of when to leave a foraging site in a variable environment for a predator that does not deplete its local resources. Active foraging is favored when the cost of moving is small or the difference between good and poor sites is large. The model corresponds to the behavior of two guilds of web-spinning spiders.