Environmental data are spatial, temporal, and often come with many zeros. In this paper, we included space-time random effects in zero-inflated Poisson (ZIP) and 'hurdle' models to investigate haulout patterns of harbor seals on glacial ice. The data consisted of counts, for 18 dates on a lattice grid of samples, of harbor seals hauled out on glacial ice in Disenchantment Bay, near Yakutat, Alaska. A hurdle model is similar to a ZIP model except it does not mix zeros from the binary and count processes. Both models can be used for zero-inflated data, and we compared space-time ZIP and hurdle models in a Bayesian hierarchical model. Space-time ZIP and hurdle models were constructed by using spatial conditional autoregressive (CAR) models and temporal first-order autoregressive (AR(1)) models as random effects in ZIP and hurdle regression models. We created maps of smoothed predictions for harbor seal counts based on ice density, other covariates, and spatio-temporal random effects. For both models predictions around the edges appeared to be positively biased. The linex loss function is an asymmetric loss function that penalizes overprediction more than underprediction, and we used it to correct for prediction bias to get the best map for space-time ZIP and hurdle models. Published in 2007 by John Wiley & Sons, Ltd.

Penguins rely on vision to travel and hunt at sea. Vision in marine predators, particularly those hunting phototactic prey under a broad range of light intensities, must be better understood to realize how these species respond to changes in their environment. We studied the effects of daily cycles in light intensity on visual predators by examining the duration and timing of chinstrap penguins' PjrgosceUs antarctica foraging trips and the size, composition, and timing of their meals. We used radio telemetry and stomach-contents sampling to study adult penguins that were provisioning chicks during the summers of 1993 and 1994 at Seal Island, Antarctica. The penguins rarely initiated or terminated foraging trips at night, but otherwise varied the timing and duration of trips to sea. Cluster analyses using departure and arrival times revealed 5 distinct modes of foraging: 3 were strictly diurnal (early, mid-, and late) and 2 were partly nocturnal (overnight and extended). Durations of diurnal trips (4 to 11 h) were shorter than overnight (13 to 14 h) and extended trips (18 to 22 h). Early and rniddiurnal trips and extended trips were significantly shorter in 1993 than in 1994; late diurnal and overnight trip durations did not differ between years. Diurnal foraging was most common in 1993, whereas overnight foraging predominated in 1994. Shortened diurnal foraging in 1993 appears to have increased the frequency of diurnal foraging by allowing more parent birds to alternate diurnal trips within a single day and by reducing the incidence of birds extending diurnal foraging through the night. That penguins foraged more frequently by day when permitted by shorter trip durations (in 1993) suggests that they opted to forage diurnally whenever possible. Returning dlurnal and overnight foragers had greater than 99 and 74 % Antarctic krill Euphausia superba by weight in their stomachs, respectively However, overnight foragers also returned with significant amounts of highly digested remains of pelagic fish, suggesting birds were in offshore waters talung fish during the night. In contrast, only 1 out of 40 diurnal foragers from both years combined had evidence of fish. Thus, the daily light cycle affected both the timing and duration of chinstrap penguin foraging as well as the type of prey consumed during trips to sea.

Observers with the University of Alaska Southeast conducting shore-based counts of harbor seals in Johns Hopkins Inlet, Glacier Bay, Alaska. H arbor seals (Phoca vitulina richardsi) inAlaska occupy a geographically extensive range and topographically diverse haul-out habitats. They are present in U.S. waters from approximately 172°E to 130°W (over 3,500 km east to west) and from 51°N to 61°N (over 1,000 km north to south), hauling out on a variety of substrates including sand, rock, and ice. Aerial surveys of harbor seals are most often conducted when peak numbers are hauled out, which usually occurs during the seals' annual molt during late summer. These surveys utilize low-altitude (100-300 m) photographs of harbor seal groups, from which seal counts are made.Alaska In Glacier Bay, harbor seal numbers declined by 75% (-14.5%/yr) from 1992 to 2002 at terrestrial resting sites and by 64% (-9.6%/yr ) from 1992 to 2001 in Johns Hopkins Inlet, Glacier Bay, the primary breeding site, which is a glacial fjord.Surveying seals in glacial fjords is difficult because the ice upon which seals haul out moves, large expanses of scattered ice offer little spatial reference to aid in counting seals, and there is often insufficient maneuvering room for low-altitude aerial surveys in the fjords. Because it is estimated that 10% or more of harbor seals in Alaska use glacial ice habitats during the molting season (AugustSeptember) each year, there is a pressing need to develop reliable survey techniques to assess harbor seal abundance in such areas. Here we evaluate two such survey methods: shore-based counts and largeformat aerial photography.