Intraocular muscles of the Canadian river otter and Canadian beaver and their optical function

1989 ◽  
Vol 67 (2) ◽  
pp. 469-474 ◽  
Author(s):  
K. A. Ballard ◽  
J. G. Sivak ◽  
H. C. Howland
Keyword(s):  
Ciliary Body ◽  
Castor Canadensis ◽  
Optical Function ◽  
River Otter ◽  
Microscopic Anatomy ◽  
River Otters ◽  
Refractive Power ◽  
Lutra Canadensis ◽  
Corneal Refractive Power

The gross morphology and microscopic anatomy of the ciliary and iris musculature of the Canadian river otter (Lutra canadensis) and Canadian beaver (Castor canadensis) were studied to help evaluate whether either species has an exaggerated accommodative mechanism for use underwater. The intraocular muscles of the otter are of a size and organization indicative of an extreme lens-deforming accommodative ability involving both the ciliary body and iris. By contrast, the intraocular muscles of the beaver eye indicate that accommodation is not significant in this animal. Thus, the intraocular musculature of the class Mammalia is not homogeneous, even within the amphibious mammals. Refractive and corneal measurements on two living river otters confirm that this animal is capable of an accommodative range that can neutralize the loss of corneal refractive power when the eye is in water.

Food habits of the river otter Lutra canadensis in the marine environment of British Columbia

1984 ◽  
Vol 62 (1) ◽  
pp. 88-91 ◽  
Author(s):  
G. B. Stenson ◽  
G. A. Badgero ◽  
H. D. Fisher
Keyword(s):  
British Columbia ◽  
Marine Environment ◽  
Food Habits ◽  
River Otter ◽  
River Otters ◽  
Two Samples ◽  
Lutra Canadensis ◽  
Fish Remains ◽  
Coastal British Columbia

Food habits of river otters (Lutra canadensis) inhabiting coastal British Columbia were studied by examining scat and stomach samples. Fish remains occurred in 99.4% of the scats while crustacean and bird remains were encountered in 7.2 and 4.2%, respectively. The majority of fish identified belong to six groups: Embiotocidae (occurring in 42.2% of the scats), Cottidae (40.5%), Pleuronectiformes (40.0%), Blennioidea (33.3%), Scorpaenidae (30.1%), and Hexagrammidae (13.1%). Of 69 stomachs collected by trappers, 86.9% contained remains of fish and 13% contained bird remains. Only two samples (2.9%) contained crustacean remains. Similar families of fish were found in both scat and stomach samples. Scat samples, collected on 10 consecutive visits to 55 sites from May 1977 through February 1978, indicated that, with the possible exception of bird remains, food types do not appear to vary seasonally. Otters in the marine environment utilize their habitat in the same manner that freshwater otters do; they are opportunistic feeders and rely primarily on midsize, slower moving fish that occur in the intertidal and subtidal regions close to shore.

scholarly journals Occupancy of Semi-Aquatic Mammals in an Urban Landscape

2021 ◽  
Author(s):  
Devin Hoffer ◽  
Clayton Nielsen ◽  
Andrew Rutter ◽  
Stefano Anile
Keyword(s):  
Forest Cover ◽  
Castor Canadensis ◽  
Single Species ◽  
Lontra Canadensis ◽  
River Otter ◽  
Occupancy Models ◽  
Lake County ◽  
River Otters ◽  
Restoration Practices ◽  
Aquatic Mammals

Abstract Throughout midwestern North American ecosystems, semi-aquatic mammals including beaver (Castor canadensis), mink (Neovision vision), muskrat (Ondatra zibethicus), and river otter (Lontra canadensis) co-exist in wetlands. These species are ecologically important through their manipulation of habitats and interactions with other species present. Although natural resource managers in urban ecosystems are interested in semi-aquatic mammals and factors affecting their ecology, few such studies exist in the literature. We studied impacts of restoration practices and other environmental covariates on detection and occupancy of the 4 aforementioned focal species on forest preserves managed by the Lake County Forest Preserve District (Lake County, Illinois, USA). Sign surveys were conducted during December-April in 2018-19 and 2019-20. We quantified 12 variables representing bank measurements, temperature, precipitation, soil type, and survey replicate to inform the detection process and quantified 12 variables representing forest cover measurements, aquatic plant measurements, dominant landcover, restoration practices, and anthropogenic disturbances for the occupancy process. Single species, multi-season occupancy models were run in RStudio using the package unmarked. Detection probabilities ranged from 0.10 ± 0.07 for river otters to 0.60 ± 0.03 for muskrats; occupancy probabilities ranged from 0.28 ± 0.18 for river otters to 0.90 ± 0.05 for muskrats. Detection and occupancy were influenced by similar environmental factors (bank measurements, precipitation, and survey replicate for detection; and stream measurements and food availability for occupancy) compared to more rural locations. We provide further evidence that muskrats are urban adapters and document the initial stages of river otter recolonization in the Chicago Metropolitan Area.

River otter hair structure facilitates interlocking to impede penetration of water and allow trapping of air

2005 ◽  
Vol 83 (5) ◽  
pp. 649-655 ◽  
Author(s):  
John W Weisel ◽  
Chandrasekaran Nagaswami ◽  
Rolf O Peterson
Keyword(s):  
Light Microscopy ◽  
Thick Layer ◽  
Air Bubbles ◽  
River Otter ◽  
Adjacent Level ◽  
River Otters ◽  
Lutra Canadensis ◽  
Microscopy Images ◽  
Scanning Electron ◽  
Size And Structure

Unlike many other mammals spending a considerable amount of time in water, river otters (Lutra canadensis (Schreber, 1777)) do not have a thick layer of body fat. Instead, they have a very densely packed layer of thin underhairs. The structure of river otter hair was examined by scanning electron microscopy and polarizing light microscopy. Guard hairs were hollow and became thicker distally and then tapered to a point and had different cuticle scales in proximal and distal regions. The cuticle of the thin underhairs had a striking pattern of sharply sculpted fins with deep grooves between them; usually there were four fins at each level, rotated 45° with respect to those at an adjacent level. Underhairs varied in diameter and the scales were sometimes petal-shaped. Polarizing light microscopy images showed interlocking arrangements of the underhairs that help to impede the penetration of water. Also, these images showed that the grooves between fins or petals of underhairs entrap air bubbles. The structure of the hairs allows them to interact loosely with each other, despite variations in size and structure. Furthermore, the nature of the interactions between the fins and depressions allows space between the hairs that can trap air bubbles to increase the thermal insulation of the otter's coat.

Corneal refractive power after myopic LASIK

Ophthalmology ◽  
2003 ◽  
Vol 110 (9) ◽  
pp. 1857 ◽  
Author(s):  
Louis E Probst ◽  
Jack T Holladay
Keyword(s):  
Refractive Power ◽  
Corneal Refractive Power

scholarly journals A River Otter's, Lontra canadensis, Capture of a Double-crested Cormorant, Phalacrocorax auritus, in British Columbia's Gulf Island Waters

2007 ◽  
Vol 121 (3) ◽  
pp. 325
Author(s):  
Michael H. H. Price ◽  
Clare E. Aries
Keyword(s):  
Lontra Canadensis ◽  
Phalacrocorax Auritus ◽  
River Otter ◽  
Freshwater Lakes ◽  
Marine Bird ◽  
River Otters

Direct and apparent predation events by River Otters (Lontra canadensis) on birds have been recorded on marine islands and freshwater lakes. We add to this the first known observation of a River Otter capturing a marine bird on the ocean.

scholarly journals River Otter Distribution and Food Habits in Grand Teton National Park as Part of an Ongoing Project in the GYE

2015 ◽  
Vol 38 ◽  
pp. 75-78
Author(s):  
Kelly Pearce ◽  
Tom Serfass
Keyword(s):  
National Park ◽  
Activity Patterns ◽  
Public Support ◽  
Primary Objective ◽  
Camera Traps ◽  
Lontra Canadensis ◽  
Flagship Species ◽  
River Otter ◽  
Grand Teton National Park ◽  
River Otters

Grand Teton National Park is part of the known range of the North American river otter, however not much is known about this semi-aquatic mammal within the park. The results presented here are part of a larger project to investigate the potential of the river otter (Lontra canadensis) to serve as an aquatic flagship (species that engender public support and action) for the Greater Yellowstone Ecosystem. River otters, known for their charismatic behavior have the potential to serve as an aquatic flagship species to promote conservation of aquatic ecosystems. The primary objective of this portion of the study was to identify river otter latrines on portions of the Snake River, between Flagg Ranch and Jackson Lake, and between Jackson Lake Dam and Pacific Creek, collect river otter scats to determine diet of the river otter, and employ remote cameras to determine activity patterns of the river otters. Between 20 June and 1 July 2015, 26 river otter latrines were identified during shoreline surveys, 186 river otter scats were collected, and cameras were deployed at 6 latrines between 7 July and 24 August 2015. River otter scats have been cleaned and prepared for analysis, but have not all been processed to date. Camera traps recorded 222 images, of which 7% (n = 14) were of carnivores, 70% (n = 155) were of non-carnivore mammals, and 9% (n = 22) were of birds. River otters were detected at 1 of the 6 latrines, a total of 5 independent times during the study.

Predation by River Otters (Lutra canadensis) on Juvenile Coho Salmon (Oncorhynchus kisutch) and Dolly Varden (Salvelinus malma) in Southeast Alaska

1993 ◽  
Vol 50 (2) ◽  
pp. 312-315 ◽  
Author(s):  
C. Andrew Dolloff
Keyword(s):  
Coho Salmon ◽  
Oncorhynchus Kisutch ◽  
River System ◽  
Dolly Varden ◽  
Salvelinus Malma ◽  
Southeast Alaska ◽  
River Otters ◽  
Juvenile Salmonids ◽  
Dolly Varden Salvelinus Malma ◽  
Lutra Canadensis

The effect of predation by river otters (Lutra canadensis) on juvenile coho salmon (Oncorhynchus kisutch) and Dolly Varden (Salvelinus malma) in a Southeast Alaska watershed was inferred by examining the number and size distribution of sagittal otoliths that were found in otter scats. Individual scats contained up to 408 otoliths, indicating that at least 200 fish had been eaten between defecations. Otoliths from juvenile salmonids outnumbered those from coastrange sculpins (Cottus aleuticus) by about six to one. Based on examination of over 8000 otoliths found in otter scats, at least 3300 juvenile salmonids were eaten by two river otters and their two young in the Kadashan River system during a 6-wk period in late spring 1985.

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