Nocturnal Shelters Research Articles

Night Capture of Roosting Cave Birds by Neanderthals: An Actualistic Approach

Evidence is accumulating on the regular and systematic Neanderthal exploitation of birds. However, the motivations, mechanisms, and circumstances underlying this behavior remains little explored despite their potential implications on Neanderthal ecology and capabilities. Fossil remains of choughs (Pyrrhocorax, Corvidae) are among the most abundant in cave sites with Mousterian technology. We reviewed the evidence showing that Neanderthals processed choughs for food, and confirmed that it occurred frequently over a widespread spatial and temporal scale. This lead us to propose the hypothesis that the cave-like refuge is the keystone resource connecting Neanderthals and choughs captured at night in rocky shelters eventually used by both species. By adopting an actualistic approach, we documented the patterns of refuge use and population dynamics of communally roosting choughs, the strategies and technology currently used to capture them, and their behavioral response against experimental human predators at night. Actualistic experiments showed that large numbers of choughs can be captured without highly sophisticated tools at night regularly and periodically, due to their occupation year-round during long-term periods of the same nocturnal shelters, the constant turnover of individuals, and their high site tenacity at these roost-sites even after recurrent disturbance and predation. Captures even with bare hands are further facilitated because choughs tend to flee confused into the cavity in darkness when dazzled and cornered by human (experimental) predators. Given the extreme difficulty of daylight chough capturing in open country, nocturnal hunting with the help of fire in the roosting caves and consumption in situ are proposed as the most plausible explanations for the strong association of choughs and Neanderthals in fossil assemblages. Night hunting of birds has implications for the social, anatomical, technological, and cognitive capacities of Neanderthals.

A dark side of cleaning symbiosis: manned submersible observations

Cleaning is a ubiquitous interspecific interaction on shallow tropical, subtropical, and temperate reefs, involving hundreds of species in all ocean basins. This remarkable mutualism encompasses fish and/or shrimp “cleaners” that remove and consume organic debris, parasites, tissue, and mucus from “client” invertebrates (e.g., anemones, crabs, octopuses) and vertebrates (e.g., sharks, bony fishes, turtles, iguanas, and cetaceans. Often regarded as a facilitative interaction, cleaning may be an important driver of reef community structure. Cleaning evolved independently in several unrelated taxa, resulting in a remarkable diversity of interaction types and behaviors. Besides the burden of epibionts, wounds, and parasites, visual and tactile signaling comprise the proximate causation of cleaning interactions. However, there are a few examples of nocturnal cleaning on marine ecosystems, which always involve shrimps acting as cleaners. Here, we report on caridean shrimps (Decapoda: Caridea) cleaning four species of carnivorous fishes in the disphotic-aphotic transition zone (280–320 m depth), based on submersible observations at the continental shelf slope off Northeastern Brazil. This is the first record of shrimp-fish cleaning interactions in deep-cold waters, and our observations support the idea that tactile signaling is of foremost importance in such interactions. We hypothesize that the complex daytime behavior and other adaptations of dedicated cleaner shrimps may have evolved from incidental cleaning by shrimps seeking food on nocturnal shelters of larger fish, or on deep water, where vision plays a minor role.

Home Range and Movement Patterns of Subadult Hawksbill Sea Turtles in Southeast Florida

Abstract Subadult Hawksbill Turtles (Eretmochelys imbricata) reside on the coral reefs of Palm Beach County, Florida, but their movements and patterns of habitat use are poorly understood. In this study, six subadult Hawksbills were tracked with global positioning system (GPS)–linked satellite telemetry for a span of 102–429 days Total home ranges and within-range areas of “core” use were measured with minimum convex polygons (MCPs) and kernel density estimates (KDEs). Home-range estimates ranged 1.1–19.0 km2 (X = 10.1 km2) using MCP and 0.01–1.2 km2 (X = 0.49 km2) using the 95% KDE. Each turtle remained at or near the 15–25 m hard-bottom reef habitats of the area and exhibited strong site fidelity to centrally located core use areas (50% and 25% KDE >,0.03 km2); this was especially true at night, suggesting the repeated use of familiar refuges (shipwrecks/caves) for nocturnal shelter. Likely driven by predator avoidance, competition for a limited number of preferred refuges, or “roosts,” may restrict the...

Habitat and food utilization of the Siberian chipmunk, Tamias sibiricus, in Korea

Compared to European countries where the Siberian chipmunk (Tamias sibiricus) is an invasive species, there is a paucity of information on the ecology and natural history of Korean populations. T. sibiricus is a native species with large populations in Korea. We conducted field research during January to December 2012 in a forest habitat located in Hongcheon-gun, Gangwon-do (37° 45′ 50″ N, 127° 50′ 52″ E) in central Korea. We used both radio-tracking and capture-recapture techniques to determine home range size and nocturnal shelters. We also excavated and measured burrows and analyzed food items from caches. The mean 95 % of kernel home range size for males was 16,586 m2 (100 % of MCP = 14,129 m2) and 4,432 m2 (100 % of MCP = 4,512 m2) for females. Burrow systems typically had a nest, latrine, and food caches with tunnels. Nocturnal shelters were uncommon and co-habiting for summer sleeping and winter torpor were also rare. The primary food items in caches were chestnuts (77.0 %), Mongolian oak acorns (12.1 %), and bird’s-foot trefoil (2.1 %). The information on the ecology and natural history of the Korean subspecies of Siberian chipmunks reported in this research shows significant differences from the ecological information for the subspecies in Hokkaido Japan.

Effects of elevated temperature on coral reef fishes: Loss of hypoxia tolerance and inability to acclimate

Water temperature is expected to rise on coral reefs due to global warming. Here, we have examined if increased temperature reduces the hypoxia tolerance of coral reef fish (measured as critical [O2]), and if temperature acclimation in adults can change the resting rate of O2 consumption and critical [O2]. Two common species from Lizard Island (Great Barrier Reef, Australia) were tested, Doederlein's cardinalfish (Ostorhinchus doederleini) and lemon damselfish (Pomacentrus moluccensis). In both species, a 3°C rise in water temperature caused increased oxygen consumption and reduced hypoxia tolerance, changes that were not reduced by acclimation to the higher temperature for 7 to 22days. Critical [O2] increased by 71% in the cardinalfish and by 23% in the damselfish at 32°C compared to 29°C. The higher oxygen needs are likely to reduce the aerobic scope, which could negatively affect the capacity for feeding, growth and reproduction. The reduced hypoxia tolerance may force the fishes out of their nocturnal shelters in the coral matrix, exposing them to predation. The consequences for population and species survival could be severe unless developmental phenotypic plasticity within generations or genetic adaptation between generations could produce individuals that are more tolerant to a warmer future.

Limited movement in blue rockfish Sebastes mystinus: internal structure of home range

Home range has been estimated for a limited number of marine fishes; however, the use of space and timing of activities within the home range has rarely been studied. In addition, under- standing movement patterns of exploited fish species has been identified as a crucial science gap, impeding informed marine reserve design. We used a radio-acoustic positioning telemetry (VRAP) system to monitor detailed movements of 10 blue rockfish Sebastes mystinus around shallow rock pinnacles and stands of bull kelp Nereocystis leutkeana in central California in September 2002. The mean home range was 8783 m 2 ± 1137 SE; however, activity was highly concentrated in 1 to 3 core areas within each home range. Mean core areas measured 1350 m 2 ± 286 SE, but accounted for ~83% of activity. All core areas were centered over rock pinnacles where rockfish were highly aggregated. Individuals exhibited high site fidelity and made only brief radial excursions away from these centers or moved directly from one pinnacle to the next along defined corridors. Patterns of diel activity and nocturnal sheltering corresponded closely with nautical twilight. Cores overlapped, but estimated locations of nocturnal shelters differed significantly among individuals. Movement patterns were cor- related with wind velocity, upwelling index, water temperature and habitat structure.

Socially acquired information from chemical cues in the common lizard, Lacerta vivipara

The use of information from chemical cues about the presence of conspecifics and their social interactions may be advantageous because it allows individuals to assess the social environment in the absence of the signallers. We tested experimentally whether the selection of nocturnal shelters by juveniles of the common lizard was influenced by the scent marks from three isolated or three socially housed adult males or females, keeping constant the number of donors for all treatments. We gave each juvenile a choice between a shelter containing odours from adults and a shelter with no odour and we compared the response to odours from three adults housed singly with that to odours from three adults that had the opportunity to interact. The shelter site selection of juveniles was influenced by the odour of socially housed adult males, but not by that of isolated males, and partly depended on the mother's site of origin and the juvenile's body condition. This study shows that juveniles use social information from conspecific chemical cues and that various phenotypes may use this information in different ways.

Twilight transitions in coral reef fish: the input of light-induced changes in foraging behaviour

The timing of twilight transition behaviour of diurnal reef fish is likely to be determined by the trade-off between food intake and risk of predation. However, the correspondence between fish behaviour and light-dependent feeding is poorly documented. We used flume measurements of prey detection and consumption by small reef-dwelling zooplanktivorous fish to examine the effects of light and prey flux on the fish's in situ behaviour during twilight. Feeding rates increased from nearly nil to saturation as light level increased, corresponding to about 45 min of the morning twilight. Changes in feeding rates were mostly due to light-dependent changes in reactive distance. In the reef, fish emerged from their nocturnal shelter at lower light intensities than those at which they retreated at dusk. These light intensities at which the fish emerged and retreated in the field greatly exceeded the level required to detect prey. We examined whether the approach of measuring relative ratio of mortality risk to food gained can be applied to predict the observed patterns in the twilight transition behaviour of the fish studied. We suggest that both the times of emergence and retreat and the dawn–dusk asymmetry are the result of a direct response to temporal and spatial variations in predation risk; no evidence for fine-tuned adjustments to diel fluctuations in food availability by changes in the time of emergence and retreat was found.

Kin recognition in the common lizard

The ability to recognize parents has never been reported in species in which parents do not provide care to their young; in such species, only sibling recognition has been found. However, there may be several advantages of parent recognition, even in the absence of parental care. We investigated the ability of neonates to recognize olfactory cues from both their mother and siblings in the common lizard, Lacerta vivipara, a species without parental care. Juveniles from 264 gravid females were reared for 2 days either with their mother, with another female, or separated from all other adults. Juveniles from some families were split into two or three groups so that each juvenile was unfamiliar with a subset of its siblings. After 2 days, we offered the juveniles a choice of two nocturnal shelters: one containing a lizard odor and the other without odor. The response to the odor of an unrelated and unfamiliar adult was influenced by both the sex of the adult and the sex of the juvenile. Juveniles of both sexes recognized the odor of their mother whether they were familiar with her or not (pre-natal determinism). Juveniles recognized familiar but not unfamiliar siblings (post-natal determinism). In the wild, spatial association with kin declines shortly after birth. Thus, recognition of the mother is likely to have biological relevance. Recognition of the mother may reduce competition and/or enhance juvenile establishment.

Structure and Organization of Local Migrations in Brown Surgeonfish (Acanthurus nigrofuscus)

AbstractIn the northern Red Sea (Gulf of Aqaba, Israel), brown surgeonfish (Acanthuridae: Acanthurus nigrofuscus) migrate, in small groups, up to 1.5 km each day from nocturnal shelters to feeding sites in the morning, and from feeding sites back to shelters in the late afternoon. During the summer spawning season, groups of these fish undertake an additional migration of up to 1 km to and from sites of mass‐spawning aggregations. The total number of fish migrating to the Laromme feeding site was relatively stable (X̄ = 1018) throughout the study period (1988–1990). By contrast, the number of fish arriving at the Lighthouse spawning site fluctuated drastically (˜50‐ > 2000), with the largest number of fish recorded around the new moon and the lowest within 1–2 days of a full moon. Durations of the migrations to and from the feeding site were similar, as were the numbers of groups arriving and departing the feeding site. In contrast, the duration of migration and number of groups were much greater during arrivals at the spawning site than during departure, due to an explosive emigration from the site following mass spawning. Arrival and departure routes differed at both feeding and spawning sites, demonstrating that simple route‐reversal is not practiced by these fish. Exchanges of position by leading and following fish in groups were rare, suggesting that leadership may play important roles in determining specific routes. Surgeonfish returning from spawning in early evening ceased migrating at a specific time, rather than a specific place, and completed their homeward‐bound migrations the next morning.

Tree hollows as a resource for wildlife in remnant woodlands: spatial and temporal patterns across the northern plains of Victoria, Australia

Hollows in living or dead trees are an important resource for a range of animal species in Australia. They are used for diurnal and nocturnal shelter and as breeding sites, and the availability of hollows may be a limiting factor for some populations. This study examined patterns in the distribution of tree hollows at 185 sites, each of 1.0 ha, in remnant woodlands across the northern plains, Victoria, a rural region where little remains of the natural woodland cover. Spatial and temporal variation in the abundance of tree hollows is evident at several scales including that of the individual tree, the landscape and the region. For individual trees, the number of holes increased with tree diameter, and the slope of this relationship differed between tree species. The percentage of trees that are hollow-bearing also differs between species. Large trees have a higher proportion of holes with a large entrance diameter (>10 cm) and a lower proportion of small holes (?2 cm diameter) than do small trees. At the landscape scale, hollow-bearing trees were not evenly distributed throughout remnant woodlands. Significant variables in a regression model of the abundance of hollow-bearing trees included: the number of large trees (>70 cms diameter), woodland tree species composition and mean annual rainfall. At the regional scale, the availability of hollows is influenced by the patchy distribution of remnant woodlands. Large tracts are mainly associated with public land along river systems and contrast with extensive areas of farmland where woodlands are sparse or absent. The abundance of hollows at the landscape and regional scale is strongly influenced by the impact of land management on two key processes; the loss of existing hollow-bearing trees and the recruitment of new trees. On privately managed land, generally grazed by domestic stock, large trees with hollows are often present, but the scarcity of saplings and small trees raises concern over the recruitment of future hollow-bearing trees, and indeed the long-term persistence of woodland vegetation. Conversely, most sites in large blocks of public land have ample regeneration but relatively fewer hollow-bearing trees due to the loss of larger trees from timber harvesting activities. In both situations, the abundance of trees with hollows is the consequence of management practices, and their future availability is directly amenable to management action. Some implications of the patterns of distribution of hollows for wildlife are discussed.

The Fish Connection: A Trophic Link Between Planktonic and Rocky Reef Communities?

The blacksmith (Chromis punctipinnis), an abundant pomacentrid fish off southern California, regularly forages on zooplankton during the day and shelters in rocky reefs at night. This behavioral pattern results in the importation of 8 grams of carbon per square meter per year, deposited as feces in the nocturnal shelter. Since blacksmiths regularly return to the same shelters, this represents a transport of extrinsic organic carbon to the reef which is predictable in time and space.

Temperature-Independent Morning Emergence in Lizards of the Genus Phrynosoma

An investigation of the relationship of morning emergence and body temperature in Phrynosoma demonstrated a rhythmic anticipation of conditions favorable for normal activity. Such a rhythm offers a mechanism by which ectothermic reptiles can use safe nocturnal shelters without loss of activity time in the morning.