Time-lapse cinematography of feather stars (Echinodermata: Crinoidea) on the Great Barrier Reef,Australia: demonstrations of posture changes,locomotion, spawning and possible predation by fish

Aspects of feather star behavior and ecology were recorded by time-lapse cinematography approximately 1 frame min^-1 on the Great Barrier Reef, Australia over a 1 mo period in 1983. The current regime influenced body postures of most species studied, whether nocturnal or not. Moreover, feather stars of several species crawled on the substratum with their arms; each crawling episode lasted roughly 10 min, and the maximum speed attained was about 1 arm length min^-1. Nocturnal feather stars crawled to their nighttime feeding perches around dusk and crawled back to their daytime hiding places around dawn. Surprisingly, some species of feather stars living on the reef surface both day and night also crawled around at dawn and dusk for reasons that are not known. In the time-lapse films, and individual of Comanthus bennetti (sex undetermined) spawned for about 2 min just after dark on 5 July 1983. Another film showed possible predation on a feather star (Himerometra robustipinna) by a saddled coralfish (Chaetodon ephippium).     

Vertical distribution and feeding patterns of midwater fish in the central equatorial Atlantic

Fishes and zooplankton were obtained (March–April 1979 and partly in August 1974) from 45 hauls taken during the day and at night in the central equatorial Atlantic between Latitude 3°N and 2°S from the surface to 1250-m depth, using the RMT 1+8, a combined opening-closing plankton and micronekton trawl. The vertical distribution of 30 myctophid species is described. All species migrate in a diel pattern, Ceratoscopelus warmingii and Lampanyctus photonotus down to at least 1250 m. During daytime most species aggregated at 400-to 700-m depth, therefore only partly occupying the depth of the Deep Scattering Layer (400 to 500 m at 15 kHz). The feeding patterns of seven of the most abundant species were compared, with a total of 1 905 stomach contents being analysed. All seven species are regarded as opportunistic predators, which feed predominantly during the night on calanoid copepods. A total of 66 species of calanoid copepods were identified among the prey items, with smaller species definitely being in the minority. Stomachs of C. warmingii (700 to 1 250 m depth) and Lepidophanes guentheri (500 to 900 m depth) from daytime samples contained copepod species restricted to the upper 150 m of the water column, including Undinula vulgaris, Nannocalanus minor, and Euchaeta marina, thereby confirming an extended vertical migration of predators. Differences in diet and preferences between species in their total food spectrum are described.     

Der einfluß des lichtes auf Körperfärbung und dämmerungsverhalten des korallenfisches Chaetodon melanotus

The influence of light on colour patterns and behaviour of the coral-reef fish Chaetodon melanotus were investigated under aquarium and field conditions. Colour pattern and fin position are correlated with agonistic behaviour: they were used as criterion for analysing the behavioural patterns during morning and evening transition.Readiness for attack is correlated with a darkening of the analfin. A specimen with yellow anal fin and spread dorsal fin is more likely to flee. The colour patterns vary during day, twilight, and night time. The speed of colour change was measured experimentally; it appears to be hormonally regulated. During twilight, 5 different colour patterns are related with certain anal-fin colour-patterns and dorsal-fin positions. Swimming activity decreases with reduction in irradiance, while the readiness to flee increases. In groups, specimens become more territorial with diminishing day light. Territorial aggression can be light-dependent; no territorial aggression was observed at illuminations less than 50 lux. Behaviour and concomitant coloration-changes during the evening and morning transition periods are interpreted as adaptational protections against predators. The remarkable white eyespots in the twilight body-coloration could represent a warning signal, and could also have a somatolytic effect. The increased readiness to flee during dusk and dawn may be a behavioural mechanism for reducing predator pressure.     

Biomasses,catch rates and abundances of demersal fishes,particularly predators of prawns,in a tropical bay in the Gulf of Carpentaria,Australia

The demersal fish fauna of Albatross Bay, in the eastern Gulf of Carpentaria, northern Australia, was sampled on seven cruises from August 1986 to November 1988, using a random stratified trawl survey. Four depth zones between 7 and 45 m were sampled during both day and night. The mean biomass of fish from all seven cruises was 297 kg ha^–1 for days trawls and 128 kg ha^–1 for night trawls. The overall mean catch rates were 922 kg h^–1 for day trawls and 412 kg h^–1 for night trawls. There were marked differences between cruises in both the biomass and catch rate. Approx 890 000 fish of 237 species were collected. Of these, 25 species comprised 82% of the total biomass and 74% of the overall catch rate. The dominant families were Leiognathidae, Haemulidae and Clupeidae, with Sciaenidae and Dasyatidae important at night.Leiognathus bindus was the most abundant species. Twenty-five species occurred in more than 50% of trawls, withCaranx bucculentus the most frequently caught (96% of all trawls). Thirty four species were predators on prawns; their absolute mean biomass was 50 kg ha^–1 during the day and 39 kg ha^–1 at night. The corresponding catch rates were 171 and 125 kg h^–1. Multiple-regression analyses were used to discriminate the effects of diel, seasonal, depth and cruise patterns. Of the 31 most abundant species, 15 showed diel patterns of abundance; 11 species showed seasonal patterns of abundance; 23 species had differential depth distribution; and 13 species showed significant cruise-to-cruise variation in abundance. Cruise variations in abundance were tested against salinity, temperature, tidal exchange, plankton biomass and prawn abundances as well as periods (and lags) of total rainfall prior to sampling. Only total rainfall showed any significant correlation. Total rainfall over a period of 6 wk immediately prior to sampling showed significant positive correlations with the abundances of five species, with overall daytime catch rates, and with the suite of 34 prawn predators. Rainfall and river runoff into Albatross Bay were significantly correlated. In Albatross Bay, the complex of factors affecting fish abundances and the magnitude of between-cruise differences indicate that such tropical communities may be unpredictable and are not seasonally constant. The high catch rates in Albatross Bay relative to similar tropical areas elsewhere are discussed and attributed to the light exploitation of the Albatross Bay stocks. Other than a prawn fishery, there is no commercial trawling in Albatross Bay. Hence, the only fishing mortality is a result of by-catch from prawn trawling. The annual total of such fish by-catch is probably less than 10% of the estimated standing stock of 93 000 tonnes.     

Circadian shelter occupancy patterns and predator–prey interactions of juvenile Caribbean spiny lobsters in a reef lagoon

The spiny lobster, Panulirus argus, is predominantly nocturnal, remaining inside shelters during the day and foraging outside at night, presumably to minimize predation risk. Predation risk generally decreases with increasing lobster size. Therefore, this study examined the hypothesis that size would influence this basic circadian pattern. Video cameras continuously recorded the shelter occupancy of juvenile lobsters (n = 72) having a carapace length (CL) of 30–62 mm that were tethered to shelters in a shallow reef lagoon. The lobsters’ shelter occupancy was 100% during the day, but declined linearly from shortly before sunset to a minimum of 50% shortly after midnight and then increased linearly, reaching 100% by 1 h after sunrise. The percent time the lobsters spent in the shelters followed a similar trend, but there was wide variability at night (0–100%) for individual lobsters. Lobsters left their shelters 2–30 times night⁻¹, with a majority of excursions lasting <10 min. These results suggest that juvenile P. argus minimize predation risk by remaining in their shelters as long as possible but offset the energetic cost of this behavior by foraging close to their shelters for several short periods at night. This emergence pattern contrasts with those of early benthic phase lobsters (<15 mm CL), which seldom leave their shelters, and adults (>80 mm CL), which have a dusk/early evening peak in activity and leave the shelter for extended periods of time during the night. Furthermore, a minimum shelter occupancy in the middle of the night appears especially well adapted to avoid exposure to daytime predators. Videotaped observations also included interactions between lobsters and two dominant lobster predators, the triggerfish, Balistes capriscus, and the octopus Octopus cf. vulgaris. Lobsters responded differently to these predators: remaining in the shelter when attacked by a triggerfish and fleeing the shelter when attacked by an octopus. Triggerfish were nearly twice as likely to attack a lobster that was outside of the shelter than inside. Once under attack, however, a lobster had nearly the same chance of surviving if it was inside or outside. Results suggest that the patterns of shelter use and emergence change as lobsters grow, probably reflecting the interplay between perception of predation risk and the need to forage. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Activity rhythms of two cirolanid isopods from an exposed microtidal sandy beach in Uruguay

Activity rhythms of two cirolanid isopods, Excirolana armata and Excirolana braziliensis, were studied based on both seasonal field observations and laboratory experiments, at an exposed microtidal sandy beach in Uruguay. The natural emergence patterns of both species were observed in the field for 1 year, twice in each season, and correlated to sea level, expected tidal cycles and diel cycles. Laboratory experiments were carried out in order to detect endogenous rhythms of activity and observe how emergence of both species was affected by changes in light and/or sediment thixotropy. We also compared behavioral strategies of sympatric species that occupy different beach levels. Sea level (and thus swash zone position) during field sampling did not follow expected tidal cycles for most sampling occasions. E. armata was observed in activity most of the time, but activity only correlated with sea level on three out of eight occasions, and only once was correlated to expected tidal cycle. Laboratory results showed that emergence under constant conditions was rare; changes in sediment thixotropy stimulated emergence, but the response was not cyclical; light had little effect on this response. On the other hand, E. braziliensis was fairly scarce in the water column, but swimming individuals were observed always during the night. They displayed an endogenous circadian activity pattern in the laboratory which augmented in response to changes in sediment thixotropy. The natural light/dark cycle modulated both spontaneous and response emergence by increasing day/night differences in activity. In this study E. armata, a midlittoral species more exposed to sea level variations, seemed to rely entirely on different physical and/or biological cues to trigger emergence at the appropriate time. E. braziliensis, found mostly in the upper intertidal zone, emerged in a circadian rhythm, which was stimulated by changes in sediment thixotropy and reinforced by light cycles. The results of this study led us to conclude that on microtidal, unpredictable beaches, local physical and biological factors can combine to determine different activity strategies in organisms from different intertidal levels. Received: 23 March 2000 / Accepted: 30 August 2000     

Patterns in the emergence of green (<Emphasis Type="Italic">Chelonia mydas</Emphasis>) and loggerhead (<Emphasis Type="Italic">Caretta caretta</Emphasis>) turtle hatchlings from their nests

The emergence patterns of both green (Chelonia mydas) and loggerhead (Caretta caretta) turtle hatchlings were observed in great detail over three seasons at Alagadi beach, northern Cyprus. In total, 38 green turtle and 50 loggerhead turtle nests were monitored, accounting for the emergence of 2,807 and 2,259 hatchlings, respectively. We quantified these emergences into 397 green turtle and 302 loggerhead turtle emergence groups. Overall, 85.0% of green turtle and 79.5% of loggerhead turtle groups emerged at night; these accounted for 85.5 and 90.8% of hatchlings, respectively. The remaining emergences were dispersed throughout the day for green turtle nests but confined to the morning in loggerhead turtle nests. Hatchling emergence from individual nests occurred over periods of between 1 and 7 nights, with most hatchlings typically emerging on the first night. Group sizes of green turtles emerging during the day were significantly smaller than those emerging at night. Hatchlings of both species that emerged from nests during the day had longer emergence durations than those that emerged from nests at night only.Communicated by R.J. Thompson, St. Johns     

Reproduction in five species of crinoids at Lizard Island,Great Barrier Reef

Reproduction in five species of crinoids [Himerometra bartschi (A. H. Clark), H. robustipinna (P. H. Carpenter), Cenometra bella (Hartlaub), Colobometra perspinosa (P. H. Carpenter), and Oligometra serripinna (P. H. Carpenter)] was studied at Lizard Island, Queensland, over 24 mo, from April 1981 to March 1983 (except for O. serripinna —June 1981 to March 1983). All five species of crinoids were dioecious, although a few instances of synchronous hermaphroditism were noted in H. bartschi, C. perspinosa, and O. serripinna. Gonad morphology and the sequence of developmental stages were similar in each species. Within individuals, gametogenesis was synchronous in gonads both along and between arms, except in some proximal and distal genital pinnules in which gonads never matured. Within a species, there was a degree of synchrony of gametogenesis in a sample, but the level of gametogenic activity varied considerably between years. A high level of continuous reproductive activity was observed in H. bartschi, H. robustipinna, Cenometra bella, and Colobometra perspinosa from about mid-summer to early/mid-winter, while O. serripinna probably had a bimodal reproductive cycle with peaks around February and June. There was a significant 1:1 male:female sex ratio in the populations sampled, and unsexable individuals were significantly smaller (as determined by maximum arm length) than either sexable males or females.     

Changes in amphipod densities among macroalgal habitats in day versus night collections along the Western Antarctic Peninsula

Amphipods along the western Antarctic Peninsula appear to gain refuge from predators by associating with chemically defended macroalgae rather than palatable macroalgae. However, nothing is known about amphipod activity at night. If foraging on non-chemically defended macroalgae regularly occurs, then nocturnal foraging seems beneficial since visual predators are disadvantaged. To test this hypothesis, we collected three common macroalgal species and affiliated mesograzers, approximately 3 h before and after sunset. All associated mesofauna were counted and densities recorded. Amphipod densities were significantly decreased during the night on the chemically defended Desmarestia menziesii, while significantly increased on the palatable Iridaea cordata. Additionally, the amphipod Gondogeneia antarctica was found in significantly higher densities at night on Palmaria decipiens, a species shown to be readily eaten by G. antarctica and omnivorous fish. We believe that chemically defended macroalgae act as a refuge for mesograzers during the day, while more widespread foraging occurs at night.     

Environmental stress,competition and dominance of Crassostrea virginica near Beaufort,North Carolina,USA

Observations and experiments were made at 2 intertidal areas near Beaufort, North Carolina, USA from May 1977 to July 1978 to determine why the oyster Crassostrea virginica dominated the community in areas protected from wave action but not in areas directly exposed to waves. Barnacles, oysters, the green alga Enteromorpha sp. and the mussel Brachiodontes exustus were the main occupiers of primary space at the mid and low intertidal levels of exposed areas. The intertidal community at the protected site consisted of a mid intertidal occupied by the barnacles Balanus amphitrite and Chthamalus fragilis, and the oyster C. virginica, and a low intertidal dominated by C. virginica. The exposed area was highly variable with high colonization and mortality for all species producing large seasonal changes in structure. The protected site remained constant throughout the year; there was no evidence of further colonization of either barnacles or oysters and mortality was very low. Recolonization experiments, selective removal of species, and growth and survival data demonstrated that C. virginica does not become dominant at exposed locations because (1) the constant wave shock at the ocean site reduces growth and increases mortality of young and adult oysters and (2) oysters are outcompeted by the mussel B. exustus. The monopolization of space by C. virginica at protected sites contrasts with studies north of Cape Hatteras where the abundance of predators produces a more diverse and heterogeneous community. Predation was unimportant in Beaufort because predators were absent at the exposed areas and the oyster drill Urosalpinx cinerea was restricted to the subtidal zone at the protected site. This absence of predators indicates a higher level of environmental stress near Beaufort compared to areas farther north.     

Diel variation and seasonal consistency in the fish assemblage of the non-estuarine Sulaibikhat Bay,Kuwait

In the period between September 1986 and August 1988, using an otter trawl, a total of 50 species from 30 families were captured in Sulaibikhat Bay, Kuwait. The dominant species were Liza carinata (Valenciennes), Pomadasys stridens (Forrskal) and Leiognathus brevirostris (Valenciennes). Although the total number of fishes captured in 1986–1987 and 1987–1988 differed by an order of magnitude, the seasonal changes in numbers, biomass and number of species in the intertidal and subtidal zones were consistent. Unbalanced three-way analysis of variance showed that significantly larger numbers of fishes and number of species, but not biomass, were captured in the intertidal at night compared to the intertidal during the day. This difference may be due to both increased net efficiency and movement of fishes into the intertidal zone at night to avoid piscivorous fishes that move from deep water into shallower water. During the day few fish are present in the intertidal zone and this may be to avoid predation by piscivorous birds. Several species of fishes were shown to have different patterns of behaviour during the diel period.     

Species composition, biomass and vertical distribution of micronekton over the mid-slope region off southern Tasmania, Australia

Seasonal sampling was carried out based on day/night, vertically stratified tows (100 or 125 m strata) in the upper 900 m of the water column over the mid-slope commercial fishing grounds south of Tasmania. A large midwater trawl (105 m² mouth area) was used with an opening/closing cod-end. Subtropical convergence and subtropical species dominated the fauna, but many less abundant, more widely-distributed species were also present. Fishes, which contributed 89% of micronekton biomass and 135 of 178 species, were dominated by the Myctophidae (48% biomass and 48 species). Twenty micronekton species made up 80% of the total biomass. Overall, the micronekton fish biomass in this region was 2.2 g m⁻² wet weight. A pronounced day/night shift in the distribution of biomass was attributable to diel migratory species. During the day, <0.2% of the total micronekton biomass was found in 0 to 300 m; most biomass was below 400 m, with peaks at 400 to 525 m and 775 to 900 m. At night, 53% of the biomass was found in 0 to 300 m, with progressively less in each deeper stratum. The vertical ranges of individual species typically exceeded 400 to 500 m during the day and night and were non-coincident, although nyctoepipelagic migrators were concentrated in the surface 200 m at night. Distinct epipelagic, lower and upper mesopelagic assemblages were identified, and patterns of epipelagic migration, limited migration and non-migration were categorised for species from each of the lower and upper mesopelagic assemblages. The vertical distribution of these assemblages was coincident with the primary water masses: subantarctic mode water (∼250 to 600 m) and antarctic intermediate water (below ∼700 m). The flux of migrating micronekton, estimated at 0.94 to 3.36 g C m⁻² yr⁻¹ to the lower mesopelagic and 1.14 to 4.06 g C m⁻² yr⁻¹ to the upper mesopelagic, appeared to be considerably outweighed by the consumption needs of aggregated mid-slope benthopelagic predators. We suggest that advection of mesopelagic prey in antarctic intermediate water may sustain aggregated populations of orange roughy (Hoplostethus atlanticus) and other predators on the micronekton in mid-slope depths at this site. Received: 2 April 1997 / Accepted: 21 August 1997     

Going deep: common murres dive into frigid water for aggregated,persistent and slow-moving capelin

Owing to the necessity of delivering food to offspring at colonies, breeding seabirds are highly constrained in their foraging options. To minimize constraints imposed by central-place foraging and to optimize foraging behavior, many species exhibit flexible foraging tactics. Here we document the behavioral flexibility of pursuit-diving common murres Uria aalge when foraging on female capelin Mallotus villosus in the northwest Atlantic. Quite unexpectedly, being visual foragers, we found that common murres dived throughout the day and night. Twenty-one percent of recorded dives (n = 272 of 1,308 dives) were deep (≥50 m; maximum depth = 152 m, maximum duration = 212 s), bringing murres into sub-0°C water in the Cold Intermediate Layer (CIL; 40–180 m) of the Labrador Current. Deep dives occurred almost exclusively during the day when murres would have encountered spatially predictable aggregations of capelin between 100 and 150 m in the water column. Temperatures within the CIL shaped trophic interactions and involved trade-offs for both predators and prey. Sub-0°C temperatures limit a fish’s ability to escape from endothermic predators by reducing burst/escape speeds and also lengthening the time needed to recover from burst-type activity. Thus, while deep diving may be energetically costly, it likely increases certainty of prey capture. Decreased murre foraging efficiency at night (indicated by an increase in the number of dives per bout) reflects both lower light conditions and changing prey behavior, as capelin migrate to warmer surface waters at night where their potential to escape from avian predators could increase.     

Predation,recruitment and the dynamics of communities of coral-reef fishes

I investigated the ability of predators to influence the patterns of species richness and abundance of non-piscivorous fishes on small, artificial reefs replenished by natural recruitment. Periodic removal of predators effectively reduced the species richness and abundance of predators on removal reefs. The difference between the number of predators on control and removal reefs was greatest immediately following the removal of predators and attenuated between removals. During periods of recruitment, species richness and total abundance of recently-recruited, non-piscivorous fishes were generally greater on predator-removal reefs than on control reefs. Species richness and total abundance of resident non-piscivorous fishes were not affected by the removal of predators in the first year of the experiment. Both abundance and species richness of residents, however, were greater on the removal reefs during the second year of the experiment. The difference in the responses of the two age classes to the removal of predators suggests that predators may affect community patterns of older age classes through time-lagged effects on the survivorship of younger age classes. At the end of the experiment, species richness was positively related to abundance for recruits and residents. The effects of removing piscivorous fishes on the abundance of non-piscivorous fishes were similar for species considered separately. A greater number of species of recruit and resident fishes were more abundant on reefs from which predators had been removed. These data suggest that predators can play an important role in structuring communities of fishes on coral reefs.     

Variability in the gut contents of individual A cartia tonsa from waters off Southern California

The gut contents of 169 individual Acartia tonsa from Los Angeles Harbor, California, USA, were measured during a 24 h period (16–17 June 1986) by gut pigment (fluorescence) and microscopic analyses. Individual gut-pigment levels varied 10-fold or more within sampling intervals. Some copepods with moderate (0.2 to 0.5 ng) to high (>0.5 ng) gut-pigment levels were present in samples from both day and night collections. While the percentage of copepods containing>0.5 ng pigment was about the same during the day (8%) as at night (10%), the percentage of copepods with 0.2 to 0.5 ng pigment rose from 17% during the day to 55% at night. Significant differences between pigment levels in copepods collected before and after evening twilight were suggestive of a nocturnal feeding habit regardless of intense individual variability in gut-pigment content. Food in the gut was distributed in parcels, indicative of intermittent feeding that potentially contributes to individual variability. Feeding was not synchronized during most of the day and night, but synchrony increased at evening and morning twilights. Although synchrony declined after evening twilight, individual gut-pigment contents were relatively elevated in most of the nighttime samples. Thus, active feeding seems neither to require nor to imply synchrony.     

Recognising one’s enemies: a functional approach to risk assessment by prey

Little has been done to compare the relative importance of various mechanisms through which prey assess the potential risk from natural enemies. We used predator-naive spider mites (Tetranychus urticae, Tetranychidae) to (1) compare the responses of prey to chemical cues from enemy and non-enemy species and (2) investigate the source of these cues. In the laboratory, we observed the distribution of T. urticae in response to cues from nine mite species, including (1) predators of spider mites, (2) predators/parasites of other animals, and (3) fungivores/pollen-feeders. When given a choice over 24 h, spider mites foraged and oviposited in fewer numbers on leaf discs that were previously exposed to predatory or parasitic mites (including species incapable of attacking spider mites) than on clean leaf discs (unexposed to mites). Interestingly, previous exposure of leaf arenas to fungivores and pollen-feeders had no significant effect on spider mite distribution. We then observed the response of T. urticae to cues from two species of predator that had been reared on a diet of either spider mites or pollen. T. urticae showed stronger avoidance of leaf discs that were previously exposed to spider-mite-fed predators than of discs exposed to pollen-fed predators. Nevertheless, for one predator species (Amblyseius andersoni), T. urticae still preferred to forage and oviposit on clean (unexposed) discs than on discs exposed to pollen-fed predators. Protein-derived metabolic wastes of predatory or parasitic mites may provide a general cue about potential predation risk for T. urticae. However, T. urticae also avoided areas exposed to pollen-fed predators, suggesting there may be other sources of enemy recognition by the spider mites. We discuss the ecological and evolutionary mechanisms that may influence the scope of information through which animals assess predation risk. Received: 11 January 1999 / Received in revised form: 25 October 1999 / Accepted: 20 November 1999     

Emergence pattern of loggerhead turtle (<Emphasis Type="Italic">Caretta caretta</Emphasis>) hatchlings from Kyparissia Bay,Greece

The present study describes the emergence pattern of loggerhead sea turtle hatchlings (Caretta caretta) from a nesting beach in Kyparissia Bay (Greece). We try to establish the role played by hatchling biometry, nest relocation and distance from nest to the sea on this emergence pattern. We surveyed a total of 32 nests, and found long emergence periods (mean = 6.7 nights). The majority of emergences occurred at night, mainly between 0030 and 0100 hours, and in small groups. Most of the hatchlings emerged from the nests the first night. We found no clear trend when we studied the effect of hatchling biometry between successive emergence days. We also found that relocation of the nests did not significantly affect the emergence pattern. However, we noted that in the relocated nests, hatchlings emerged in smaller groups. Emergence periods were inversely related to distance from the sea. In short, factors such as climate conditions, relocation and nest distance to the sea appear to have some effect on the emergence pattern. Therefore, they should be taken into account in both biological studies and management plans for sea turtle nesting beaches. Our results suggest leaving an extended period between the first emergence of hatchlings and the excavation of nests by researchers in future studies in the area.     

Field survey of the occurrence and significance of regeneration in Amphiura filiformis (Echinodermata: Ophiuroidea) from Galway Bay,west coast of Ireland

The Boreo-Mediterranean amphiurid Amphiura filiformis (O. F. Müller) occurs in high densities within Galway Bay. This burrowing species consistently shows signs of recent regeneration (of both arms and disc “cap”) at the above locality. Specimens were collected by SCUBA in March, April and May 1980, May 1981, and April 1982. Biomass assays have revealed that individuals with up to 50% (mean ca. 25%) of their entire body weight consisting of regenerated tissue are not uncommon. The occurrence of arm breakage and regrowth was found to be more frequent in the proximal (basal) and mid-arm regions than in the exposed arm tip portions. Roughly 3% of the population were found to be in the process of regenerating the disc “cap” or covering. Preliminary results from gut analyses of potential predators at the sampling station indicate that young flatfish (plaice and dab) actively “crop” the arms of A. filiformis. Records from north western Europe of this species occurring in the diets of fish and invertebrates are considered. In this long-lived species, the continual necessity to regenerate is deemed to be a major drain on bodily resources.     

The effects of nesting stage,sex, and type of predator on parental defense by killdeer (Charadrius vociferous): testing models of avian parental defense

Summary Two models predicting the temporal patterns of parental investment in offspring defense over the nesting cycle were tested. The first is based on offspring age, the other on the vulnerability of offspring to predation. Both models make very similar predictions for altricial species after eggs have hatched, i.e., increases in intensity of parental defense until fledging. For precocial species, however, the post-hatching predictions of each model are different: the offspring age model predicts a continued increase in defense intensity, while the vulnerability model predicts a decline. I examined the temporal patterns of parental defense of a precocial shorebird, the killdeer (Charadrius vociferus), and determined which model was supported. Killdeer responses to human and natural predators were observed. Killdeer were less willing to leave the nest, responded most intensely, and displayed closest to a potential predator around hatching. Defense intensity increased from early to late incubation as predicted by the offspring age model. However, after hatching killdeer parental defense declined for both males and females, thus supporting the vulnerability model for this stage. Males and females responded significantly differently to all types of predators. Males took greater risks, remained on the nest longer, defended offspring more intensely, and displayed closer to the predator than females at the approach of a potential predator. Responses to natural predators depended on the type of predator and the approach made by the predator; a greater range of defense behavior was used for predators approaching on the ground compared to aerial predators. In general, killdeer responses to humans were more intense and less variable than their responses to natural predators. This was most likely because the human intruder approached nests and chicks more directly and closer than natural predators.     

Spatial and temporal patterns of habitat use by Eurasian oystercatchers (<Emphasis Type="Italic">Haematopus ostralegus</Emphasis>) in the eastern Wadden Sea revealed using GPS data loggers

Detailed knowledge on species–habitat relationships is of crucial importance for the understanding of processes in marine ecosystems. Being top-predators, birds are important bio-indicators for marine systems. The aim of this study was to elucidate precise information on foraging habitat use and foraging times of oystercatchers (Haematopus ostralegus) on wide tidal flats using global positioning system (GPS) data loggers. The study was conducted to collect hints for the negative population trends in oystercatchers in the Wadden Sea. It is the first time that GPS technique has been used in a shorebird species. Although oystercatchers are known to exhibit foraging site fidelity, a number of individuals visited multiple sites. Foraging trips at night were longer, and the targeted sites were further away than those used during the day. These patterns were likely to be caused by higher risks of clutch predation by avian predators during the day that led adults to reduce their absence to defend their clutches. Our methodological approach enabled the subtle spatio-temporal patterns of habitat use to be determined on a very fine spatio-temporal scale. We suggest further potential studies using GPS data loggers that may help to reveal the reasons for the current declines in oystercatcher populations in the German Wadden Sea.