Nest Type Research Articles

Mixed species flock, nest height, and elevation partially explain avian haemoparasite prevalence in Colombia.

The high avian biodiversity present in the Neotropical region offers a great opportunity to explore the ecology of host-parasite relationships. We present a survey of avian haemoparasites in a megadiverse country and explore how parasite prevalences are related to physical and ecological host characteristics. Using light microscopy, we documented the presence of haemoparasites in over 2000 individuals belonging to 246 species of wild birds, from nine localities and several ecosystems of Colombia. We analysed the prevalence of six avian haemoparasite taxa in relation to elevation and the following host traits: nest height, nest type, foraging strata, primary diet, sociality, migratory behaviour, and participation in mixed species flocks. Our analyses indicate significant associations between both mixed species flocks and nest height and Haemoproteus and Leucocytozoon prevalence. The prevalence of Leucocytozoon increased with elevation, whereas the prevalence of Trypanosoma and microfilariae decreased. Plasmodium and Haemoproteus prevalence did not vary significantly with elevation; in fact, both parasites were found up to 3300m above sea level. The distribution of parasite prevalence across the phylogeny of bird species included in this study showed little host phylogenetic signal indicating that infection rates in this system are evolutionarily labile. Vector distribution as well as the biology of transmission and the maintenance of populations of avian haemoparasites deserve more detailed study in this system.

Reproductive biology of Pleurodema guayapae (Anura: Leptodactylidae: Leiuperinae).

Pleurodema guayapae is a species that inhabits saline environments and semidesert zones from central Argentina. To date, the knowledge about the reproductive biology of this species is very poor, and our aim is to contribute to its knowledge with the description of some important reproductive aspects. For this, field work was undertaken in an area near to Patquia, La Rioja province. Sampling was undertaken during three summer periods (2006-2007; 2007-2008; 2008-2009) in Chamical-Patquia area, where we could find reproductively active populations. We observed and described breeding sites, type of clutch, process of foam nest construction, clutch and egg number and sizes, and hatching time and stage. Behaviour observations were performed from the time that males began to call until the pairs ended up the foam nests building, and layed the eggs. Additionally, one amplected pair was observed and filmed in the process of foam nest construction, and four amplectant pairs were collected and separatelly placed in plastic containers, for nests observations in the laboratory. Hatching time was based on three different foam nests of known age. We found that P. guayapae populations were acoustically active only after a rainfall. Its breeding sites were represented by ephemeral ponds of fresh water, product of rains. The males emitted their calls inside or outside these ponds. A detailed description of the foam nest construction process by both females and males was made. The clutches were in dome-shaped foam nest type of 6-9cm in diameter and 1-3cm in height, some of which were in communal nests. The nests had an average of 1 137 pigmented eggs. This species showed a short hatching time. Our results allow us to conclude that this species should be considered an extreme explosive breeder. Our results are discussed with others obtained for related species.

Does nest size matter to laying hens?

Laying hens in loose housing systems have access to group-nests which provide space for several hens at a time to lay their eggs. They are thus rather large and the trend in the industry is to further increase the size of these nests. Though practicality is important for the producer, group-nests should also cater to the egg-laying behaviour of hens to promote good welfare. One of the factors playing a role in the attractiveness of a nest is the amount of enclosure: hens prefer more enclosure when having a choice between different nest types. The aim of this study was to investigate if hens prefer smaller group-nests to lay their eggs given that they may seem more enclosed than larger nests.The relative preference of groups of laying hens for two nest sizes – 0.43m2 vs. 0.86m2 – was tested in a free-access choice test. The experiment was conducted in two consecutive trials with 100 hens each. They were housed from 18 to 36 weeks of age in five groups of 20 animals and had access to two commercial group-nests differing in internal size only. We counted eggs daily as a measure of nest preference. At 28 and 36 weeks of age, videos were taken of the pens and inside the nests on one day during the first 5h of lights-on. The nest videos were used to record the number of hens per nest and their behaviour with a 10min scan sampling interval. The pen videos were observed continuously to count the total number of nest visits per nest and to calculate the duration of nest visits of five focal hens per pen.We found a relative preference for the small nest as more eggs, fewer nest visits per egg and longer nest visit durations were recorded for that nest. In addition, more hens – including more sitting hens – were in the small nests during the main egg-laying period, while the number of standing hens did not differ. These observations indicate that even though both nests may have been explored to a similar extent, the hens preferred the small nest for egg-laying.

Evidence of philopatry and natal dispersal in Humboldt Penguins

We report evidence of both philopatry and natal dispersal in Humboldt Penguins (Spheniscus humboldti) from a colony in central Chile. Between 1994 and 2001, we tagged 241 Humboldt Penguin chicks with subcutaneous transponder chips. Seven birds (3%) were found as adults at their natal colony: five were breeding (philopatric birds) and two were prospecting for nest-sites. Another four birds (2%) were found breeding at other colonies up to 90 km from the natal colony. Philopatric birds bred at 3.6-6.1 years old (mean ± s.d. = 4.8 ± 1 years) at nests located 5–80m from their natal nests (30 ± 25 m). Most philopatric and the prospecting birds used the same types of nests as their natal ones and we suggest that birds breeding for the first time may use cues of structural aspects of their natal nest when choosing a nesting site for the first time.

Extreme microclimate conditions in artificial nests for Endangered African Penguins

SummaryAfrican Penguins Spheniscus demersus naturally breed in guano burrows which provide shelter from predators and extreme weather conditions. Past guano harvesting has removed this habitat and artificial nests of different types have been deployed, with previous research identifying variable success of these different types. We investigated climatic conditions in two types of artificial nests, and compared them to natural burrows and surface nests for two weeks in the incubation and early chick-rearing phases of the 2012 summer breeding season on Bird Island, Algoa Bay, South Africa. We also compared breeding success since 2009 between some of these nest types. Natural burrows remained the best insulated from extremes of temperature and humidity, with temperatures consistently higher and humidity consistently lower than in exposed nests and the two types of artificial nests. Fibreglass nests retained temperatures > 30°C, when Spheniscus penguins start being heat-stressed, for the longest periods of time. Sustained high temperatures will induce increased energy expenditure associated with active thermoregulation for birds in these nests. The combination of high temperatures and low humidity could also have contributed to damaging water loss in the eggs and reduced egg survival, as suggested by the consistent lower hatching success in the fibreglass nests. Cement nests had more moderate temperatures than fibreglass nests and higher breeding success, possibly due to superior ventilation. Vegetation cover had no effect on the temperature regime inside fibreglass nests. To maximise conservation efforts for these endangered penguins, additional research should be conducted towards engineering artificial nests that better mimic the conditions of natural burrows.

Eavesdropping cuckoos: further insights on great spotted cuckoo preference by magpie nests and egg colour

Reproductive success of brood parasites largely depends on appropriate host selection and, although the use of inadvertent social information emitted by hosts may be of selective advantage for cuckoos, this possibility has rarely been experimentally tested. Here, we manipulated nest size and clutch colouration of magpies (Pica pica), the main host of great spotted cuckoos (Clamator glandarius). These phenotypic traits may potentially reveal information about magpie territory and/or parental quality and could hence influence the cuckoo's choice of host nests. Experimentally reduced magpie nests suffered higher predation rate, and prevalence of cuckoo parasitism was higher in magpie nests with the densest roofs, which suggests a direct advantage for great spotted cuckoos choosing this type of magpie nest. Colouration of magpie clutches was manipulated by adding one artificial egg (blue or cream colouration) at the beginning of the egg-laying period. We found that host nests holding an experimental cream egg experienced a higher prevalence of cuckoo parasitism than those holding a blue-coloured egg. Results from these two experiments suggest that great spotted cuckoos cue on magpie nest characteristics and the appearance of eggs to decide parasitism, and confirm, for the first time, the ability of cuckoos to distinguish between eggs of different colours within the nest of their hosts. Several hypothetical scenarios explaining these results are discussed.

Nest position and type affect predation rates of artificial avian nests in the tropical lowland forest on Mount Cameroon

Nest predation is the leading cause of reproductive failure in birds and thus it shapes their life history strategies. Intensities of nest predation appear to differ among nest locations and types in both temperate and tropical regions. However, there is limited knowledge of factors influencing susceptibility of avian nests to predation in Africa. The aim of our study was to investigate artificial nest predation rates of different ground and shrub nests located at different heights in the rainforest undergrowth. We placed artificial avian nests within a homogeneous lowland forest interior with sparse forest undergrowth in the Mount Cameroon National Park, Cameroon. We exposed three sets of nests: 50 bare-ground, 50 cup-ground and 50 cup-shrub nests, for 10 d. Predation was higher for cup-ground nests compared to cup-shrub nests, and bare-ground nests were more depredated than cup-ground nests. We concluded that the presence of a cup as well as higher nest position significantly increased probability of artificial nest survival. The results of this study suggest a potential selection pressure on nest type and placement in lowland forest birds for a poorly known tropical region.

Termite nests as an abundant source of cultivable actinobacteria for biotechnological purposes.

A total of 118 actinobacterial isolates were collected from the three types of termite nests (mound, carton, and subterranean nests) to evaluate their potential as a source of bioactive actinobacteria with antimicrobial activity. The highest number (67 isolates) and generic abundance (7 known genera) of actinobacterial isolates were obtained from carton nests. Streptomyces was the dominant genus in each type of termite nest. In the non-Streptomyces group, Nocardia was the dominant genus detected in mound and carton nests, while Pseudonocardia was the dominant genus in subterranean nests. A discovery trend of novel species (<99% similarity in the 16S rRNA gene sequence) was also observed in the termite nests examined. Each type of termite nest housed >20% of bioactive actinobacteria that could inhibit the growth of at least one test organism, while 12 isolates, belonging to the genera Streptomyces, Amycolatopsis, Pseudonocardia, Micromonospora and Nocardia, exhibited distinct antimicrobial activities. Streptomyces sp. CMU-NKS-3 was the most distinct bioactive isolate. It was closely related to S. padanus MITKK-103T, which was confirmed by 99% similarities in their 16S rRNA gene sequences. The highest level of extracellular antimicrobial substances was produced by the isolate CMU-NKS-3, which was grown in potato dextrose broth and exhibited a wide range (6.10×10−4–1.25 mg mL−1) of minimum inhibitory concentrations against diverse pathogens. We concluded that termite nests are an abundant source of bioactive strains of cultivable actinobacteria for future biotechnological needs.

Pilomatricoma: an unusual presentation.

Dear Editor: Pilomatricoma, a slow-growing, benign adnexal tumor of the skin, originates from primitive cells of the hair matrix. It usually appears as a painless, firm, subcutaneous nodule, which adheres to the overlying skin. The overlying skin normally has a bluish discoloration. Although lesions with bullous changes on the overlying skin are very rare, they have been reported1,2,3. Herein, we report a case of bullous pilomatricoma to enhance the recognition and proper management of this variant, which represents a particular diagnostic challenge. An 18-year-old woman chiefly complained of a slightly tender, bullous skin lesion on her right upper back (Fig. 1A). Three months earlier, the lesion had appeared as a painless, firm nodule that enlarged with time beneath the skin. The bullous appearance was detected 1 month before her visit. The bulla was thick-walled, semitransparent, and sized 2.5×3 cm. A palpable mass was faintly noted inside the bulla. Systemic and laboratory examination results were normal. Preoperative bulla bisection revealed a firm central tissue core, surrounded by a sac and serous fluid (Fig. 1B). The lesion was totally excised and closed directly. The 1×2 cm mass inside the bulla was similar to a classical pilomatricoma: well demarcated, lobulated, and hard. On microscopic examination, we observed typical cells; anucleate keratinized basaloid cells (Fig. 2A, B). Endothelial cells of the dilated lymphatic channels were positive, on immunohistochemical staining, for CD34 and D2-40. Pseudocysts without endothelial cell lining were noted in the superficial dermis (Fig. 2C). The patient remained well without recurrence during follow-up for six months. Fig. 1 (A) Preoperative photograph showing the semi-transparent bulla, sized approximately 2.5×3 cm, with a whitish nodule inside, located on the right upper back of the patient. (B) Appearance inside the bulla: a firm central tissue core, within a serous ... Fig. 2 (A) Scanning view (1:1) demonstrating the whole architecture of the tumor with cystic change (H&E). Microscopic finding shows multiple dilated lymphatics above the typical nests of shadow cells and basophilic cells. (B) Arrow indicates ghost cells, ... Reports on bullous pilomatricoma are limited. To date, a total of 18 cases have been published1. Bullous pilomatricoma has a predilection for the shoulder and upper arm regions, predominantly affecting women aged 10 to 20 years. Lymphatic fluid fills the bulla-like space. It has been postulated that the pressure surrounding the hard core of the pilomatricoma induces obstruction of lymphatic vessels and congestion of lymphatic fluid, resulting in dilation of lymphatic vessels, with leakage of lymphatic fluid, and edema in the dermis surrounding the tumor, producing a bullous appearance2. Nearly all the cases of bullous pilomatricoma are formed by typical tumor nests-composed of shadow and basophilic cells-surrounded by a fibrotic capsule. Most cases present dilated lymphatic vessels and lymphedema in the superficial dermis2,3. Ghost, or shadow, cells are the most characteristic microscopic findings in pilomatricoma cases. They have distinct cell borders, with eosinophilic cytoplasm and a central clearing, representing the outline of an absent nucleus. Commonly, there is an associated foreign-body multinucleated giant-cell reaction and fibrosis with calcification; hence, this lesion was originally described as calcifying epithelioma of Malherbe. As for the classical pilomatricoma, surgical excision is the treatment of choice because this lesion does not regress spontaneously. The prognosis is excellent, without reported recurrences or malignant changes after excision.

Nest relocation in the ant Pheidole dentata

We studied nest relocation in the ant Pheidole dentata, a common species in the southern US, by following colonies for 6 weeks. We correlated probability of relocation with several abiotic and biotic environmental factors, such as air temperature, humidity, leaf litter depth (LLD), nest type and presence of phorid fly parasitoids. Colonies moved often, on average every 16.2 days. By the end of our study, fewer than 5 % of colonies marked at the start remained in their original nests. Only 3.1 % of colonies returned to a previously used nest. The mean distance of relocation was 0.76 ± 0.73 m. Colonies nested in a variety of locations, such as in the ground, by tree trunks, under rocks and inside wood. Several factors affected probability of relocation. Higher LLD and vapor pressure deficit (VPD) increased probability of relocation. Probability of relocation varied by nest type, by plot and week of study. We found no evidence that surface cover or rain affected relocation behavior. Colonies appear to avoid nests that become dry by nesting against tree trunks. Phorid fly abundance correlated negatively with VPD, yet it had no effect on colonies’ likelihood of relocation. We discuss other implications of frequent nest relocations.

Nest site selection and efficacy of artificial nests for breeding success of Scarlet Macaws Ara macao macao in lowland Peru

Psittacidae (parrots) have the most threatened species of any bird family in the world. Most parrots are obligate secondary cavity nesters, and can be limited in their breeding success by the availability and quality of nest hollows. However, nesting opportunities for parrots can be increased by provision of artificial nest boxes. The Tambopata Macaw Project has been studying the breeding ecology and natural history of the Scarlet Macaw Ara macao macao in the south-eastern Peruvian Amazon for over 20 years by monitoring natural nest hollows and two types of artificial nest (wooden and PVC). We present data for breeding success in natural and artificial nests over 12 consecutive breeding seasons. The aims of this study were to: (a) determine the nesting requirements and reproductive success of breeding macaws; and, (b) compare the efficacy of the two types of artificial nests and natural nest cavities. Our data showed a high rate of reoccupation of successful nests in consecutive years and that nests in artificial and natural nests had very similar reproductive parameters. Our results indicate that artificial nest types can be used by conservation managers seeking to assist A. macao populations where nest hollows are in short supply, and that artificial nests can contribute important data to natural history studies of species where access to natural nests is limited.

Nest Types and Microhabitat Characteristics of the Japanese Marsh WarblerLocustella pryeri

Nest form and nesting habitat are important for a bird's breeding success due to their influence on the risk of breeding failure. The Japanese Marsh Warbler Locustella pryeri, which breeds in wet grasslands under habitat management, builds three types of nests: deep-cup Type I, domed Type II without decoration, and domed Type III decorated with live grasses. Relationships among nest types, habitat management, and nesting microhabitat characteristics were examined in the Hotokenuma wetland in northern Japan. During the breeding seasons in 2007–2010, a total of 263 nesting attempts were monitored, and 16 Type I, 61 Type II, and 25 Type III nests were measured. Prescribed burning affected the determination of nest type, and warblers built Type III nests frequently after burning. The microhabitat around the nests differed among the three nest types. Type II nests were constructed in wet conditions with abundant dead understory vegetation. In contrast, Type III nests were built in dry conditions with abundant live understory vegetation. Type I nests showed characteristics intermediate between those of the two domed types and were also found in spots with abundant hard stems. Nest type, habitat management, and nesting microhabitat did not affect nest predation or breeding success. We conclude that nest type differs depending on the characteristics of the nesting habitat.

Conditional Use of Social and Private Information Guides House-Hunting Ants

Social animals can use both social and private information to guide decision making. While social information can be relatively economical to acquire, it can lead to maladaptive information cascades if attention to environmental cues is supplanted by unconditional copying. Ants frequently employ pheromone trails, a form of social information, to guide collective processes, and this can include consensus decisions made when choosing a place to live. In this study, I examine how house-hunting ants balance social and private information when these information sources conflict to different degrees. Social information, in the form of pre-established pheromone trails, strongly influenced the decision process in choices between equivalent nests, and lead to a reduced relocation time. When trails lead to non-preferred types of nest, however, social information had less influence when this preference was weak and no influence when the preference was strong. These results suggest that social information is vetted against private information during the house-hunting process in this species. Private information is favoured in cases of conflict and this may help insure colonies against costly wrong decisions.

Nesting patterns of European hedgehogs (Erinaceus europaeus) under northern conditions

Little information exists on the nesting of hedgehogs (Erinaceus europaeus) in the harsh northern environment, although this aspect has specific importance for the species’ survival in this region. We studied the nest types and nesting site selection of radio tagged hedgehogs in urban areas in Eastern Finland. Altogether, four different nest types were discovered and one of them (the pre-hibernation nest) is described here for the first time. Hedgehogs preferred residential areas for nesting during the mating and post-mating seasons while in the pre-hibernation season and hibernation period nesting was more common in forest areas. Nest constructions were closely related to materials found in the nest vicinity. During the active period, males used on average 24 nests and changed them 30 times, whereas females used 17 nests and changed them 26 times. The number of female nests and frequency of nest change increased from post-mating to pre-hibernation seasons, while in males both decreased. In general, female and male nests were situated within their established long-term home range, but in the pre-hibernation season over 30 % of male nests were situated outside of it. In post-mating and pre-hibernation seasons, females avoided other individuals of the same sex; this was demonstrated by the lack of nests in other female core areas. Hedgehogs hibernate for around 223 days, which is the longest reported hibernation period for this species. The results of the present study emphasise the importance of forest and diverse residential areas including forest patches for the hedgehog’s nesting habitat.

Nest predators of southeast Asian evergreen forest birds identified through continuous video recording

Using continuous video recording, we identified predation as the main cause of nest failure of understorey‐nesting birds in an intact evergreen forest in northeastern Thailand. Our dataset of 87 predation events is the largest recorded in the tropics. The main predators were macaques (n = 38; 43.7%), nocturnal snakes (n = 19; 21.8%), non‐raptorial birds (n = 12; 13.8%), raptors (n = 6; 6.9%), squirrels (n = 5; 5.7%) and tree shrews (n = 4; 4.6%). The two most important predators, Pig‐tailed Macaque Macaca nemistrina and Green Cat Snake Boiga cinerea, showed no preference for nest type, nest stage or nest height and we found no difference in their relative predation rates among years. Predation was predominantly diurnal (73.6%), suggesting that visual cues may be important for predators at this site.

Relationships between nest humidity and nest types in living archosaurs

Nest humidity (Pnest) is important for archosaur incubation because it has a direct effect on the water vapour conductance () of the eggs. Estimates of are commonly used to infer nest type in extinct archosaurs, although it is unknown whether a relationship exists between nest type and nest humidity or between nest type and . In this study, the nests of 54 living archosaur species (i.e. birds and crocodilians) were classified into three generalised nest types, including covered, non-covered cup and non-covered scrape nests, based on their nest architectures. Pnest and ambient humidity of the nesting habitat (Pa) of these species were compared among these three nest types. Statistical analyses show that Pnest is significantly higher in covered nests than in the non-covered nests, including both cup and scrape types, indicating that the covered nests are significantly more humid than the non-covered nests. Although Pa is lower than Pnest in all species, Pa is not significantly different among the three nest types. These results suggest that although Pa has a fundamental affect on Pnest (i.e. Pnest ≥ Pa), the nest humidity is affected by the architecture of the nesting materials, that is the covered nests are shown to retain more humidity than the non-covered nests.

Evaluation of artificial nests as a conservation tool for three forest-dwelling raptors

Forest age structure has become younger and the amount of old forest has decreased due to intensive forestry in Northern Europe. Consequently, large forest-dwelling hawks may lack nest sites as they need large trees to support their nests. Construction of artificial nests has been a globally adopted conservation measure to provide nest sites for several raptors, but the impact of this practice has seldom been evaluated. We compared the nesting success of northern goshawk Accipiter gentilis, common buzzard Buteo buteo, and honey buzzard Pernis apivorus in natural and artificial nests based on long-term data in Finland. The probability of successful nesting of goshawk and common buzzard was lower in artificial nests, whereas no difference was found in the nesting success of honey buzzard between the nest types. Brood size did not differ between natural and artificial nests in successful nests of any of the three species. Finally, distances to anthropogenic features had no effect on nesting success. These results indicate that hawks switching from natural to artificial nests are potentially lured to an ecological trap with higher risk of nesting failure. However, breeding at artificial nests, even with lower success than in natural nests, can still add to the population, if otherwise nonbreeding individuals settle to nest. It should be investigated which part of the population breeds in artificial nests and whether the site selection for artificial nests needs revision. Our results emphasize the importance of monitoring and evaluation of well-intentioned conservation efforts.

Organochlorine pesticides in nest substratum and infertile eggs of American crocodiles (Reptilia, Crocodylidae) in a Mexican Caribbean atoll

As top predators, crocodilians can bioaccumulate high concentrations of persistent organochlorine pesticides (OCPs) that may have adverse effects on their physiology and health. Recent and illegal uses of OCPs in Mexico could affect populations of the American crocodile (Crocodylus acutus), already threatened by other factors. We analyzed 16 OCP compounds using gas chromatography with electron capture detection in seven infertile eggs and in the substratum of nine nests of American crocodiles in Banco Chinchorro, an atoll off the Mexican coast of the Yucatan peninsula. Nest type, clutch size and distance from nests to nearest lagoon were also recorded, while total length of the females attending each nest was measured directly or estimated. Although Banco Chinchorro is isolated from the mainland and from known sources of contamination, OCP residues were detected in egg and nest substratum samples collected from the atoll. OCP concentrations in eggs (range: 0.002-4.000 ppb) and nest substrata (range: 0.01-1.82 ppb) are ten to thousands times lower compared to other studies. Total OCP concentration (sum of all OCPs) in nest substrata decreased with increasing distance from the shore, suggesting that eggs deposited farther from the shore were less exposed to OCP absorption from substratum. Total OCP concentrations in eggs were positively correlated with total length of females and thus with their age. We speculate that maternal transfer from laying females is likely the major source of contaminants in eggs. Future investigations are needed to identify the origin of contaminants in Banco Chinchorro.

Effects of Human Presence on Chimpanzee Nest Location in the Lebialem-Mone Forest Landscape, Southwest Region, Cameroon

In several areas of Africa, great apes experience increasing predation pressure as a result of human activities. In this study, terrestrial and arboreal nest construction among chimpanzee (Pan troglodytes ellioti) populations was investigated in the Lebialem-Mone Forest Landscape (LMFL), Southwest Region, Cameroon, to examine the anthropogenic effects on nest location. Data on the height, distribution and approximate age of chimpanzee night nests were collected during two 4-week primate field surveys (July to August 2010; July 2011) at two field sites (Bechati and Andu) within the LMFL. Data were collected using the line transect method. Chimpanzee night nests were categorized by their location: arboreal versus terrestrial. During the two field surveys, arboreal night nests were the most frequently constructed nest type at both sites, and the only type of night nest constructed at Bechati. Terrestrial night nests were also constructed at Andu. The main difference between these two sites is the level of human predation and agricultural development. At Bechati chimpanzees inhabit forest regions around dense, expanding villages and are regularly hunted by humans. However, at Andu the chimpanzee populations are not under the same threat. Therefore, terrestrial night nest construction in the LMFL appears to be a behavior exhibited where there is less human presence.

Effects of season, sex and body size on the feeding ecology of turtle-headed sea snakes (Emydocephalus annulatus) on IndoPacific inshore coral reefs

In terrestrial snakes, many cases of intraspecific shifts in dietary habits as a function of predator sex and body size are driven by gape limitation and hence are most common in species that feed on relatively large prey and exhibit a wide body-size range. Our data on sea snakes reveal an alternative mechanism for intraspecific niche partitioning, based on sex-specific seasonal anorexia induced by reproductive activities. Turtle-headed sea snakes (Emydocephalus annulatus) on coral reefs in the New Caledonian Lagoon feed entirely on the eggs of demersal-spawning fishes. DNA sequence data (cytochrome b gene) on eggs that we palpated from stomachs of 37 snakes showed that despite this ontogenetic stage specialization, the prey comes from a taxonomically diverse array of species including damselfish (41 % of samples, at least 5 species), blennies (41 %, 4 species) and gobies (19 %, 5 species). The composition of snake diets shifted seasonally (with damselfish dominating in winter but not summer), presumably reflecting seasonality of fish reproduction. That seasonal shift affects male and female snakes differently, because reproduction is incompatible with foraging. Adult female sea snakes ceased feeding when they became heavily distended with developing embryos in late summer, and males ceased feeding while they were mate searching in winter. The sex divergence in foraging habits may be amplified by sexual size dimorphism; females grow larger than males, and larger snakes (of both sexes) feed more on damselfish (which often lay their eggs in exposed sites) than on blennies and gobies (whose eggs are hidden within narrow crevices). Specific features of reproductive biology of coral reef fish (seasonality and nest type) have generated intraspecific niche partitioning in these sea snakes, by mechanisms different from those that apply to terrestrial snakes.