INTRODUCTION

Present-day Arkansas has been known for its infestations of ticks since the early 1800's. Early naturalist Thomas Nuttall (1821, p. 151) wrote in 1819 in Arkansas territory near the Red River that the woods “were now disgustingly infested with ticks...” Lancaster (1973) did the only intensive study of the ticks inhabiting Arkansas mammals and birds. Although Lancaster reported on 35 species of native and naturalized mammals, he omitted the river otter (Lutra canadensis). This semi-aquatic mustelid has one of the largest distributions of any North American mammal ( Anderson, 1977 ), yet few specimens have been collected. Most of the specimens that have been received by researchers were previously skinned and could not be examined for ectoparasites ( Chanin, 1985 ). No study has been done determining the occurrence of ticks on an adequate sample of indigenous river otters. The literature of the ticks and other ectoparasites of the other members of the subfamily Lutrinae is modest and is in obscure publications. The purpose of the present study is: 1) to determine the occurrence of ticks and other ectoparasites on Arkansas river otters, 2) to summarize the literature on the occurrence of ticks and other ectoparasites on otters (subfamily: Lutrinae), and 3) to compare the tick assemblage of otters to other mustelids plus other furbearing mammals which occur in Arkansas wetlands.

MATERIALS AND METHODS

A total of 24 river otters was obtained from fur buyers and trappers in Arkansas (trapped in December, January, February, March, April, and June). Specimen donators were requested to put their otter specimens in a plastic bag after trapping and to freeze them. The author thawed them and brushed the pelt in both directions (i.e. with the grain of the fur and against) onto a light-colored piece of paper or plastic bag in order to dislodge ectoparasites. Small recesses and other likely areas (e.g. pinnae, muzzle, groin, and axilla) were examined carefully for the presence of ectoparasites. All ectoparasites were collected and preserved in 70% ethyl alcohol. Numbers of each ectoparasite species per otter, location of ectoparasites on host, sex of ectoparasite, and collection locality, host sex, and collection date of host were recorded. Specimens were identified with the aid of keys by Cooley and Kohls (1945) and Lancaster (1973) .

RESULTS

The pelage of 24 unskinned otter specimens yielded a total of 10 ticks from 5 otters. No other macro- or micro-ectoparasites were found. Small mites may have easily been overlooked. Two species of ticks were represented; the Lone star tick (Amblyomma americanum) and the hard tick (Ixodes cookei). Table 1 lists the collection data.

Ticks occurred on both male and female otters collected in January, February, and April in areas such as the pinnae, muzzle, lip, and groin where the pelage is less dense and skin is more highly vascularized. Ticks came from river otters captured in the West Gulf Coastal Plain and the Ouachita Mountain Natural Divisions, areas in Arkansas that have the highest density of otters ( Polechla, 1987 ). No suitable specimens from the Mississippi Alluvial Plain, Ozark Mountain, and Crowley's Ridge Natural Divisions were available for inspection.

DISCUSSION

These occurrences of Ixodes cookei and Amblyomma americanum constitute new host records for Lutra canadensis and the subfamily Lutrinae. Prior to this study only seven species of ectoparasites have been identified from otters ( Table 2 ). Most authors ( Stephens, 1957 ; Johnson et al., 1967 ; Harris, 1968 ; Kenyon, 1969 ) have regarded ectoparasites to be very rare due to the otters' aquatic behavior. However, the lustrous guard hairs and wool hairs are very dense ( Peterson, 1914 ) and create a dead air space that effectively keeps the base of the pelage and skin dry ( Tarasoff, 1972 , 1974 ). This provides a suitable microhabitat for ticks, mites, a fleas, and marine sucking lice. When otters periodically surface for a breath of air, the parasitic arthropods are given an opportunity for gaseous exchange. Two factors may explain the low infestation rate usually found on otters. Otters in their vigilant grooming may rid themselves of many ectoparasites.

Some of the ticks found on otters have been found on other mustelids and wetland furbearing mammals. Ixodes cookei has been found on other furbearing mammals species occurring in wetlands with river otters (e.g. raccoons (Procyon lotor) and opossums (Didelphis virginiana) and other mustelids (e.g. badgers (Taxidea taxus), long-tailed weasels (Mustela frenata), spotted skunks (Spilogale putorius), and striped skunks (Mephitis mephitis) ( Lowery, 1974 ; Mumford and Whitaker, 1982 ; Rabinowitz, 1983 ). Ixodes hexagonus has been reported from the long-tailed weasels, minks (Mustela vison), and striped skunks ( Lowery, 1974 ). Amblyomma americanum is very common in Arkansas and has been found on 16 native and domestic mammals ( Lancaster, 1973 ) including the mustelid, the striped skunk ( Lancaster, 1973 ; Lowery, 1974 ). Nuttall (1821, p. 130) wrote that after he had taken a collecting trip that he “picked off my skin and clothes more than 50 ticks (Acarus sangisugas) which are here more abundant and trouble some than in any part of America which I have been yet.” The old specific name, Acarus sangisugas is synonymous with Amblyomma americanum.

Otters may contract ticks by making contact with conspecifics, other mammals, infested substrate, vegetation, and bedding materials. Prime sites for transfer of ticks to otters would be along wildlife trails, otter rolling sites, or beaver lodges. Otters may be important in transporting ticks across large rivers and other bodies of water.

Acknowledgements - I express my thanks to Drs. Mark Schram and J. L. Lancaster, Jr., of the University of Arkansas, Fayetteville and Dr. James E. Keirans, of the Department of Entomology, Smithsonian Institution of aid in identification. This study (No. 19 of Project W-56-54) was funded under the provisions of the Federal Aid in Wildlife Restoration Act (Pittman-Robertson Act), administered by the U.S. Fish and Wildlife Service, Department of the Interior. Funding for the Act is derived from an excise tax on sporting arms and ammunition. The Arkansas Game and Fish Commission and the University of Arkansas cooperated. Anonymous reviewers read the manuscript.

REFERENCES

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