Lack of association between magnetic patterns and the distribution of free-ranging dolphins

Clifford A. Hui

doi:10.2307/1382559

Home/Archive/USGS

USGS · 1008092

Lack of association between magnetic patterns and the distribution of free-ranging dolphins

Clifford A. Hui

View original source ↗Export metadata ↓

Abstract

While free-ranging dolphins ( Delphinus sp.) have been shown to be associated with bottom topography (depth contours of the sea floor), stranded dolphins have been shown to be associated with magnetic topography. Association with magnetic patterns that may be useful for orientation and navigation by free-ranging dolphins has not been demonstrated. Evaluation of the same 140 locations of free-ranging Delphinus delphis that demonstrate an association with bottom topography patterns shows no association with magnetic intensity gradients or directional orientation with magnetic patterns. Dolphins may be able to detect cues from both bottom topography and magnetic patterns, but the free-ranging dolphins analyzed here are associated with only bottom topography.

Explore related subjects

Journal of Mammalogy Article

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Clifford A. Hui. 1994. Lack of association between magnetic patterns and the distribution of free-ranging dolphins. https://doi.org/10.2307/1382559

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2025

Predicting niche spaces of expanding Evening Bat (Nycticeius humeralis) populations following white-nose syndrome establishment

Observations of the Evening Bat ( Nycticeius humeralis ), a species historically distributed abundantly throughout the southeastern United States, are speculated to have increased in the Midwest. One hypothesis for this expansion in geographic distribution is that local extirpations of other bat species resulted in the expanded realized niche spaces for evening bats. In Indiana, such niche spaces may have been created by declines in populations of the Northern Long-eared Bat ( Myotis septentrionalis ), Indiana Bat ( M. sodalis ), Little Brown Bat ( M. lucifugus ), Big Brown Bat ( Eptesicus fuscus ), and the Tri-colored Bat ( Perimyotis subflavus ) due to white-nose syndrome (WNS). Our goal was to estimate the occupancy of Evening Bat in Indiana post-WNS establishment relative to the occupancy of other bat species before significant population declines caused by WNS. We expected that indices of occupancy of nearly extirpated species pre-WNS establishment would best predict current Evening Bat observations, and this would elucidate the niche space evening bats are now filling. We hypothesized that Evening Bat populations may be expanding their geographic range due to compensatory community dynamics, and that their realized niche space may be expanding in part due to losses of other bat species from WNS. We constructed multi-season Bayesian occupancy models using informative priors and integrative prior knowledge to test our predictions. We found that evening bats are occupying the niche space they were already occupying pre-WNS establishment. Furthermore, our results indicate that evening bats may be filling the niche space left behind by Myotis spp. ( M. sodalis and M. lucifigus ). These results can help us understand the dynamics of bat communities in a post-WNS establishment landscape and may also help to inform conservation of imperiled Myotis species.

Journal of Mammalogy↗

USGS2025

Summer roost site suitability analyses for 4 special status bat species in the Eastern United States

Data describing habitat suitability are crucial for implementing effective conservation planning but are often lacking at regional and continental scales. We address this gap for 4 bat species that are listed, proposed for listing, or under Endangered Species Act listing review by highlighting a framework for estimating summer roost suitability with a presence-background approach to aid development of conservation policy and management plans. The 4 species of concern are the Little Brown Bat ( Myotis lucifugus ), the Northern Long-eared Bat ( M. septentrionalis ), the Indiana Bat ( M. sodalis ), and the Tricolored Bat ( Perimyotis subflavus ). Our estimates of summer roost suitability were developed for the eastern United States at a fine spatial resolution (250 m pixels) suitable for conservation planning across multiple scales. Summer roost habitat suitability was higher in areas with higher tree canopy cover for each of these species, though subtle differences were observed between the species that often use buildings (e.g., Little Brown Bat), tree crevices, cavities, and elements of dead or dying trees (e.g., Northern Long-eared Bat and Indiana Bat), and foliage (e.g., Tricolored Bat). To this end, roost suitability was not identical among species, and each showed subtly different relationships to the environmental covariates considered here. We also use a novel approach, gradient surface metrics, to quantify differences in the spatial pattern of summer roost suitability among the 4 species and found that tricolored bats and northern long-eared bats showed the most homogeneous and spatially smooth habitat suitability surfaces. Estimates of summer roost suitability developed here were also used to identify areas of good summer habitat where our models showed the least uncertainty that may be beneficial for targeted conservation, such as limiting disturbance to potential roost habitat. We also identified areas where additional data would benefit future summer roost modeling efforts. This work provides a first step toward developing multistate inventories of summer roost habitat suitable for implementing effective conservation planning at multiple scales.

Journal of Mammalogy↗

USGS2025

Context matters: Intrinsic and extrinsic factors modulate habitat choices in an endangered forest bat

Effective management of declining species depends upon fundamental understanding of habitat preferences during key life stages such as reproduction. Peripheral populations of wildlife are often poorly understood and rarely the focus of study, despite their contribution to genetic diversity and their potential to aid in recolonization if a species becomes endangered. We assessed the maternal roost-site preferences of the endangered northern long-eared bat ( Myotis septentrionalis ) within a managed forest near the western edge of their range in the Black Hills region of Wyoming, USA. We further examined whether habitat preferences and roost-switching varied by reproductive state (pregnant or lactating) or proximate weather conditions. Bats were more likely to roost in quaking aspens during pregnancy, and when weather was cooler and wetter. Conversely, bats roosted more in ponderosa pines ( Pinus ponderosa) post-parturition, and when temperatures were warmer. Bats also were more likely to switch to a new roost after periods of warmer temperature and reduced solar radiation. Our results support growing evidence that habitat choices can be modulated proximately by intrinsic and extrinsic factors. Northern long-eared bats in the Black Hills relied on a variety of roost types, from healthy live trees to snags at different decay stages depending on reproductive stage and ambient weather. Our study highlights the importance of considering diverse contexts when characterizing habitat preferences, particularly for endangered species in a rapidly changing world.

Wyoming↗