Hal Markowitz

Effects of human traffic on the movement patterns of Hawaiian spinner dolphins (Stenella longirostris) in Kealakekua bay, Hawaii

Kealakekua Bay is an important resting site for Hawaiian spinner dolphins (Stenella longirostris) and is popular with both local residents and tourists. Human activities occurring here include swimming, snorkeling, kayaking, and motor-boating. The objectives of this study were to document movement patterns of dolphin groups in Kealakekua Bay, to determine if different types and levels of human activity within the bay result in quantifiable changes in dolphin group movement patterns, and to provide baseline data for future studies. Theodolite tracking was used to assess responses of dolphin groups to human traffic. Variables examined included group mean leg speed (leg speed: the distance between two consecutive theodolite fixes of a dolphin group divided by time; mean leg speed: the average of all leg speeds comprising a track) and group reorientation rate. Swimmers and/or vessels were present within 100 m of all dolphin groups tracked during all surveys. Regression analyses were used to examine potential relationships between dolphin group related variables (e.g., reorientation rate, mean leg speed) and variables related to human activities (e.g., swimming, kayaking, motor-boating). Increasing levels of human activity had a limited but measurable effect on the movement patterns of Hawaiian spinner dolphin groups at this site.

DIURNAL VOCAL PATTERNS OF THE BLACK HOWLER MONKEY (ALOUATTA PIGRA) AT LAMANAI, BELIZE

Abstract The majority of the literature describing howling monkeys (Cebidae) has focused on only 2 of 6 species in the genus. These studies have revealed differences in behavior between species and differences within species at different locations. One study has been published describing the vocal patterns of the black howler monkey (Alouatta pigra). This species appears to differ markedly from previously described Alouatta. In an effort to further distinguish A. pigra from its congeners, we observed the vocal patterns of an additional population of black howler monkeys. This population exhibited a bimodal calling pattern similar to that previously described for A. pigra, but absent in all but one (A. fusca) of the other species in the genus. The bimodal pattern was evident in both the rainy and dry seasons, with peaks in the morning and afternoon. Midday and afternoon calling were significantly reduced in the dry season. We also made a detailed comparison between both populations to examine the function of the afternoon peak. Contrary to the results of the previous study, we conclude that there is insufficient evidence to describe either of these populations as territorial.

Foraging distribution of Pacific harbor seals (Phoca vitulina richardii) in a highly impacted estuary

Abstract Assessing the relative importance of environmental and anthropogenic influences on the distribution of wild populations is an important step in designing spatially explicit plans for their management and protection. We examined environmental variables correlated with the spatial distribution of eastern Pacific harbor seals (Phoca vitulina richardii), a marine mammal common to coastal waters, in a large, highly urbanized estuary. We assessed the relationship between prey abundance, depth, bottom relief, proximity to terrestrial haul-out sites and 3 potential sources of anthropogenic influence, and the in-water spatial distribution of seals. We identified locations of seals using satellite-linked telemetry, and used partial Mantel tests to assess which environmental variables were most strongly linked to seal foraging distribution, given spatial autocorrelation within variables. Mann–Whitney tests were used to compare environmental characteristics of locations of seals with a random distribution of locations. Because harbor seals are central-place foragers, we incorporated spatial distribution of seals relative to the central place into our analyses. High prey abundance and proximity to the haul-out site were strongly associated with the spatial distribution of seals. Harbor seals also tended to use deeper waters and areas of high bottom relief within the estuary. There was no consistent spatial relationship between the 3 anthropogenic factors and the distribution of seals, although seals tended to be found closer than expected to sites of high human activity. In highly impacted coastal areas where limited alternate suitable habitat exists, foraging seals may need to rely on disturbed (suboptimal) areas, and as a result may habituate to human presence in areas rich in food resources.

DENSITY, DISTRIBUTION, AND HOME RANGE OF THE BLACK HOWLER MONKEY (ALOUATTA PIGRA) AT LAMANAI, BELIZE

Abstract The population of black howler monkeys (Alouatta pigra) at the Lamanai Archaeological Reserve in northwestern Belize was studied for a total of 11.5 months during 2 wet and 2 dry seasons between October 1993 and May 1995. We estimated home-range size and range overlap of troops in order to examine territoriality, and tested the null hypothesis that the population is uniformly distributed throughout the reserve in order to examine habitat use. Home-range sizes were similar to those at Bermudian Landing, Belize, but smaller than those at Tikal, Guatemala. Mean home-range size was estimated as 15.3 ha with 52% overlap based on a 1.0-ha grid. There was no evidence for territoriality. Population distribution was generally uniform, but ruin sites appeared to be preferred habitat and edge habitat was least frequented.