455 research outputs found
Spatial and Oceanographic Factors Affecting Black-Legged Kittiwake and Thick-Billed Murre Distributions in the Southeastern Bering Sea
The distribution patterns of Thick-billed Murres (Uria lomvia) and Black-legged Kittiwakes (Rissa tridactyla) in the southeastern Bering Sea were documented at sea during vessel-based surveys in July-August of 2008 and 2009. The relationships of murre and kittiwake densities with environmental variables were investigated using binomial generalized additive models (GAMs) to model the presence or absence of birds, and Gamma-error distribution GAMs to model the positive densities of birds. Environmental variables included oceanographic factors (Chlorophyll, Chlorophyll anomalies, Daily SST, Monthly SST), spatial factors (Distance to nearest colony, Distance to 300m shelf break, Depth), and a temporal factor (Year). Nocturnal surveys were also conducted in 2009 using a novel surveying protocol to quantify changes in seabird distribution patterns between day and night. Diurnal and nocturnal transects were modeled with environmental variables and acoustically derived measures of prey abundance, to investigate whether birds associated with different regions or food types between day or night. The association of murres with habitat variables did not differ greatly between years, and variability in murre distributions was primarily explained by spatial factors. When pooled between years, murres sighted closest to St. Paul were positively associated with chlorophyll concentrations and with the proximity to their colony, whereas murres from St. George were positively associated with the proximity to their colony, chlorophyll concentration, and a monthly sea surface temperature of 7° Celsius. In contrast, the association of kittiwakes with habitat variables differed significantly between year and when categorized by closest colony. In 2008, kittiwake densities were not strongly associated with any variables, but were most closely related to oceanographic conditions. In 2009, kittiwake sightings were more concentrated along the shelf break and northwest of St. Paul Island over the continental shelf. Kittiwakes sighted nearest to St. George were significantly associated with shelf break habitat in both years, whereas kittiwakes sighted nearest St. Paul were more closely associated with middle shelf habitat northwest of St. Paul. The distribution of murres did not differ between day and night, but kittiwake distributions shifted to deeper water at night. Kittiwakes were positively associated with juvenile walleye pollock abundance in the top 100m during the day, but were not clearly associated with pollock at night. The nocturnal distribution of kittiwakes over deep water and near the shelf break may have reflected other nearby prey resources (myctophids, smoothtongue) that were not well-quantified. In conclusion, 2008 and 2009 were both similar “cold” environmental years during which murres appeared to use consistent foraging patterns, whereas kittiwakes associated with different habitat variables between years and frequented distinct foraging areas between day and night
Using rangefinder binoculars to measure the behaviour and movement of European Shags Phalacrocorax aristotelis in coastal environments
Rapid inversion: running animals and robots swing like a pendulum under ledges.
Escaping from predators often demands that animals rapidly negotiate complex environments. The smallest animals attain relatively fast speeds with high frequency leg cycling, wing flapping or body undulations, but absolute speeds are slow compared to larger animals. Instead, small animals benefit from the advantages of enhanced maneuverability in part due to scaling. Here, we report a novel behavior in small, legged runners that may facilitate their escape by disappearance from predators. We video recorded cockroaches and geckos rapidly running up an incline toward a ledge, digitized their motion and created a simple model to generalize the behavior. Both species ran rapidly at 12-15 body lengths-per-second toward the ledge without braking, dove off the ledge, attached their feet by claws like a grappling hook, and used a pendulum-like motion that can exceed one meter-per-second to swing around to an inverted position under the ledge, out of sight. We discovered geckos in Southeast Asia can execute this escape behavior in the field. Quantification of these acrobatic behaviors provides biological inspiration toward the design of small, highly mobile search-and-rescue robots that can assist us during natural and human-made disasters. We report the first steps toward this new capability in a small, hexapedal robot
Territory Holders Are More Aggressive towards Older, More Dangerous Floaters
Animals that show aggression often risk injury and incur steep energetic costs. Thus, aggression should occur at such times and towards such opponents as to maximize fitness. We tested hypotheses predicting adaptive territorial aggression in the common loon, a species in which ease of observation of territory owners and floaters (prebreeders) seeking to evict them provide a rare window onto owner-floater competition. As predicted, older, more competitive floaters (4-year-olds and upwards) tended to intrude into territories that had produced chicks the previous year (and, hence, were of high quality). Older floaters also showed predicted increases in aggression and territorial yodeling, and a lower rate of submissive behaviors than younger floaters. Floaters of all ages intruded more often than neighboring territory owners, as predicted, but tended to avoid territories with chicks. For their part, owners yodeled more often and behaved more aggressively during chick-rearing, although yodels peaked in frequency 2 weeks before aggression, suggesting that males with young chicks yodel to discourage intrusions, but employ aggression to protect older chicks. Territory owners showed the predicted higher rates of aggression and yodeling towards older, more dangerous floaters than towards young, submissive ones. However, territorial pairs did not treat floaters more aggressively than neighbors, overall. Moreover, owners showed no spike in aggression nor yodeling following a year with chicks, perhaps to avoid providing social information to floaters that use chicks as social information to target territories for eviction
Strutural Damage Induced by Pyritic Shale
The Evangelical Hospital located in Lewisburg, Pennsylvania has experienced distress in the form of cracked floor slabs and displaced structural steel due to swelling of the underlying fill material and natural bedrock formation. The bedrock consisted of black, pyritic, calcareous shale from the Marcellus Formation of the Hamilton Group (Devonian Age). The fill materials beneath the cracked concrete floor slabs consisted of the weathered shale fragments from this formation. Although mitigating the structural distress has been attempted, the building continued to experience problems relating to the swelling of the underlying bedrock materials. The expansion of the shale could be attributed to the oxidation of the pyrite, which produced sulfuric acid. The sulfuric acid, in turn, reacted with the calcium carbonate (calcite) in the shale partings producing the mineral gypsum. Since gypsum has approximately twice the molar volume of calcite, the result is an expansion or swelling of the shale. Various laboratory tests were conducted on the shale in an attempt to simulate the swelling processes. The failures and successes of the laboratory testing have given new directions for additional research to further educate Geotechnical Engineers unfamiliar with the expansive nature of pyritic shale
Associative Memory In Three Aplysiids: Correlation With Heterosynaptic Modulation
Much recent research on mechanisms of learning and memory focuses on the role of heterosynaptic neuromodulatory signaling. Such neuromodulation appears to stabilize Hebbian synaptic changes underlying associative learning, thereby extending memory. Previous comparisons of three related sea-hares ( Mollusca, Opisthobranchia) uncovered interspecific variation in neuromodulatory signaling: strong in Aplysia californica, immeasureable in Dolabrifera dolabrifera, and intermediate in Phyllaplysia taylori. The present study addressed whether this interspecific variation in neuromodulation is correlated with memory of associative ( classical conditioning) learning. We differentially conditioned the tail-mantle withdrawal reflex of each of the three species: Mild touch to one side of the tail was paired with a noxious electrical stimulus to the neck. Mild touch to the other side served as an internal control. Post-training reflex amplitudes were tested 15 -30 min after training and compared with pre-test amplitudes. All three species showed conditioning: training increased the paired reflex more than the unpaired reflex. However, the temporal pattern of conditioning varied between species. Aplysia showed modest conditioning that grew across the post-test period. Dolabrifera showed distinctly short-lived conditioning, present only on the first post-test. The time course of memory in Phyllaplysia was intermediate, although not statistically distinguishable from the other two species. Taken together, these experiments suggest that evolutionary changes in nonassociative heterosynaptic modulation may contribute to evolutionary changes in the stability of the memory of classical conditioning
High Spatial and Temporal Resolution Census Data Reveal Communities at Risk Along the Wildland-Urban Interface (WUI) in California, USA
We tracked census tract level population change along California\u27s wild land-urban interface (WUI) during the past decade (2010-2019), an ecological sensitive region transitioning from developed land to wilderness. Our results from Mann-Kendall analysis, a method employed for monotonic trend detection showed that about one-third (29.1%) of census tracts in California’s WUI have seen a significant population increase from 2010 to 2019, affecting 12.7% population in California. The population increase along WUI is largely driven by the sixteen counties in the San Francisco Bay Area (10) and Southern California (6). We also found that higher proportion of WUI residents in Bay Area and larger number of WUI residents in Southern California. Bay Area counties in general have a higher proportion of population living in WUI tracts with significant population increase than Southern California counties. However, the lower proportion of residents living in WUI in Southern California counties account for a much larger population. Riverside is the county with the highest number of residents living in WUI tracts that have experienced significant population increase during the past decade. These residents also account for a high proportion (29.2%) of total population in Riverside. Preliminary results showed that the increase of population along WUI is driven by the house affordability and house ownership in 16 counties of Bay Area and Southern California. These factors can still explain a significant amount of the spatial pattern if extended to all counties in California
Plunging Floater Survival Causes Cryptic Population Decline in the Common Loon
Populations of many vertebrates are declining and geographic ranges contracting, largely as a consequence of anthropogenic threats. Many reports of such decline, however, lack the breadth and detail to narrow down its causes. Here we describe population decline in the Common Loon (Gavia immer), a charismatic aquatic bird, based on systematic resighting and measurement of a marked population. During our 27-year investigation, age-adjusted chick mass has fallen by 11%, mortality among young and old chicks has increased by 31% and 82%, respectively, and fledging success has declined by 26%. Meanwhile, the return rate of marked nonbreeders (“floaters”) has plunged by 53%, and the adult population overall has declined by 22%. Consistent with the thinning ranks of floaters, the rate of territory eviction has decreased by 52% during the study. Despite the decline in floaters, territory occupancy remains unchanged. However, a matrix model, updated with recent estimates for breeding success, juvenile survival, and senescence, yields a recalculated deterministic population growth rate (λ) of 0.94 for our study population, which suggests that declines in vital rates could lead to a loss of 52% of the current population and a decline of 37% in territory occupancy by 2031. Lack of data on floaters in other upper Midwest and New England loon populations leaves their status in doubt
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