Behavioral games involving a clever prey avoiding a clever predator: An individual-based model of dusky dolphins and killer whales

Faced with an intermittent but potent threat, animals exhibit behavior that allows them to balance foraging needs and avoid predators and over time, these behaviors can become hard-wired adaptations with both species trying to maximize their own fitness. In systems where both predator and prey share similar sensory modalities and cognitive abilities, such as with marine mammals, the dynamic nature of predator-prey interactions is poorly understood. The costs and benefits of these anti-predator adaptations need to be evaluated and quantified based on the dynamic engagement of predator and prey. Many theoretic models have addressed the complexity of predator-prey relationships, but few have translated into testable mechanistic models. In this study, we developed a spatially-explicit, geo-referenced, individual-based model of a prototypical adult dusky dolphin off Kaikoura, New Zealand facing a more powerful, yet infrequent predator, the killer whale. We were interested in two primary objectives, (1) to capture the varying behavioral game between a clever prey and clever predator based on our current understanding of the Kaikoura system, (2) to compare evolutionary costs vs. benefits (foraging time and number of predator encounters) for an adult non-maternal dusky dolphin at various levels of killer whale-avoidance behaviors and no avoidance rules. We conducted Monte Carlo simulations to address model performance and parametric uncertainty. Mantel tests revealed an 88% correlation (426 × 426 distance matrix, km²) between observed field sightings of dusky dolphins with model generated sightings for non-maternal adult dusky dolphin groups. Simulation results indicated that dusky dolphins incur a 2.7% loss in feeding time by evolving the anti-predator behavior of moving to and from the feeding grounds. Further, each evolutionary strategy we explored resulted in dolphins incurring an additional loss of foraging time. At low killer whale densities (appearing less than once every 3 days), each evolutionary strategy simulated converged towards the evolutionary cost of foraging, that is, the loss in foraging time approached the 2.7% loss experienced by evolving near shore-offshore movement behavior. However, the highest level of killer whale presence resulted in 38% decreases in foraging time. The biological significance of these losses potentially incurred by a dusky dolphin is dependent on various factors from dolphin group foraging behavior and individual energy needs to dolphin prey availability and behavior.     

Renal tubular dysfunction caused by dietary hexachlorocyclohexane (HCH) isomers

Abstract

Dietary administration of β‐ and α‐hexachlorocyclohexane (HCH) to albino rats caused an abnormal excessive excretion of glucose in the urine, blood glucose level being nearly normal. Occurrence of glucosuria was also accompanied by increased excretions of the two low‐threshold compounds ‐ creatinine and urea, their levels in blood being normal. The interference of HCH isomers with renal function as evidenced by biochemical data was also indicated by histopathological lesions observed in the kidney sections, viz., hypertrophy and degeneration of the renal tubular epithelia.     

Studies on the distribution op β‐ and γ‐isombrs op hexachlorocyclohexane in rat tissues

Abstract

A study of the comparitlve distribution pattern of β‐ and γ‐isomers of hexachlorocyclohexane (HCH) in albino rat tissues as a function of duration of treatment at two dose levels revealed different accumulation patterns for the two isomers in tissues. In general, the accumulation pattern was found to be in the order: fat > kidney > lungs > liver > muscle > heart > spleen > brain > blood for β‐HCH and fat > brain > kidney > muscle > lungs > heart > spleen > liver > blood for γ‐HCH. The tissue accumulation of β‐isomer was always greater than that of γ‐isomer in any tissue except in brain. Brain β‐HCH residue levels were relatively lower than in many other tissues except blood, whereas brain γ‐HCH concentration was only next to fat. A higher dose or a longer period of treatment generally produced a more marked elevation of tissue residue levels in β‐HCH fed rats, but not in γ‐HCH treated animals.

Food restriction subsequent to a period of exposure to dietary β‐ or γ‐HCH caused a mobilization of depot fat without drastic redistribution of the HCH residues stored in it. During food restriction, the residue levels in fat and muscle increased much. The residue levels in brain and other organs were not adversely affected during partial starvation.     

Activity profile of innate immune-related enzymes and bactericidal of freshwater fish epidermal mucus extract at different pH

Environmental Science and Pollution Research - The epidermal mucus of fish performs diverse functions from prevention of mechanical abrasion to limit pathogen invasions. The current experiment was...     

An analysis of the 'Modified Sturm Test' data

The 'Modified Sturm Test' uses carbon dioxide production as the primary end point in assessing the biodegradation potential of organic chemicals. This test was conducted by a commercial laboratory to assess the potential biodegradability of an oil stabilizer sample from an oil company in Canada. There was a high percentage conversion of total organic carbon present in the sample but carbon dioxide measured was low. Many possibilities were analyzed in this paper in order to understand the situation. The analysis showed that the test was subject to criticism from the point of view of CO2 measurement, 10-day window period, and aeration/mixing conditions.     

Assessment of Calibration Parameters for an Aerial Gamma Spectrometry System using Monte-Carlo Technique

During a radiation emergency subsequent to a nuclear accident orweapon fallout, quick assessment of the ground contamination andthe resulting exposure is of prime importance in planning and execution of effective counter measures. For an online assessmentof ground contamination, it is essential to calibrate the detector system for several parameters viz. the source energy,source deployment matrix, the flight altitude and position abovethe contaminated surface. This article discusses the methodology to predict all the necessary parameters like photon fluence atvarious altitudes, the photo-peak counts in different energy windows, Air to Ground Correlation Factors (AGCF) and the doserate at any height due to air scattered gamma ray photons. Themethodology includes generation of theoretically simulated gammaspectra at a required detector position for a given source distribution on the ground using Monte-Carlo method provided by general purpose coupled neutron/photon transport code (MCNP CCC-200). Thus generated gamma spectra are analyzed to arrive at the required parameters mentioned above.     

Irrigation Reliability Under Climate Change Scenarios: A Modeling Investigation in a River‐Based Irrigation Scheme in New Zealand1

Srinivasan, M.S., J. Schmidt, S. Poyck, and E. Hreinsson, 2011. Irrigation Reliability Under Climate Change Scenarios: A Modeling Investigation in a River‐Based Irrigation Scheme in New Zealand. Journal of the American Water Resources Association (JAWRA) 47(6):1261–1274. DOI: 10.1111/j.1752‐1688.2011.00568.x Abstract: The impact of climate change (CC) on irrigation reliability in a river‐based irrigation scheme in New Zealand was investigated. Reliability was defined as the river’s ability to meet the demand. Two future periods were considered, 2030‐49 (“2040”) and 2080‐99 (“2090”), and reliability at these periods were compared against those in 1980‐99 (“current”). A hydrology model, calibrated and validated for current condition, was applied to simulate flows for CC scenarios. Annual precipitation and mean temperatures were predicted to increase under CC scenarios over current condition. Occurrence of high intensity rainfall events indicated large flows under CC scenarios, though these increases could be occurring outside the irrigation season (September‐April). Compared to current condition, under CC scenarios, the number of days per season supply falling below demand could increase by 5 (2040) to 17% (2090). Snow storage plays a major role in sustaining flows in early spring under current condition. However, with increasing temperatures under CC scenarios, the average annual snow water storage could decrease from 155 mm (current) to 97‐134 mm (2040) and 40‐90 mm (2090). Under CC scenarios, to sustain the current levels of land and water uses in this scheme, storage options need to be explored.     

Biochemical changes produced by beta- and gamma-hexachlorocyclohexane isomers in albino rats

Administration of beta- and gamma-isomers of hexachlorocyclohexane (HCH) at 800 ppm dietary level for 2 weeks to albino rats produced noticeable hepatocellular damage as indicated by elevations in serum aminotransferases and decreases in hepatic soluble enzymes. Although serum total LDH activity was not altered, the LD5 isoenzyme was proportionately higher in the HCH isomers treated animals. Treatment of rats with beta- and gamma-isomers of HCH increased the hepatic glucose-6-phosphate dehydrogenase and aldolase activities suggesting a higher rate of glucose oxidation. Liver glucose-6-phosphatase activity was decreased in these animals indicating inactivation of gluconeogenesis in liver. Dietary beta- and gamma-HCH decreased the liver mitochondrial DNP/Mg++/Ca++-activated ATPases thus affecting the energy metabolism. An unaltered ratio of DNP/Mg++-ATPase, a study of swelling pattern of hepatic mitochondria, and NAD+ permeability test suggested the maintenance of structural integrity of mitochondrial membrane in these pesticide fed animals. Liver microsomal Na+,K+-ATPases were lower in these animals.