The Taxonomic Status of Wild Canis (Canidae) in the South Central United States Author(S): Howard Mccarley Source: the Southwestern Naturalist, Vol

Southwestern Association of Naturalists

The Taxonomic Status of Wild Canis (Canidae) in the South Central United States Author(s): Howard McCarley Source: The Southwestern Naturalist, Vol. 7, No. 3/4 (Dec. 15, 1962), pp. 227-235 Published by: Southwestern Association of Naturalists Stable URL: http://www.jstor.org/stable/3668845 . Accessed: 24/05/2013 18:39

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions THE SOUTHWESTERN NATURALIST 7 (3-4): 227-235 DEC. 10, 1962

THE TAXONOMICSTATUS OF WILD CANIS (CANIDAE) IN THE SOUTH CENTRAL UNITED STATES HOWARD MCCARLEY

Departmentof Biology, Austin College, Sherman, Texas

ABSTRACT. The relationshipbased on skullmorphology of populationsknown as Canis latransand C. nigerin Arkansas,Louisiana, Oklahoma and Texas is considered.Available evidenceindicates that C. niger has becomeextinct except in isolatedareas of Louisiana.Elsewhere, C. latranshas replacedC. nigeras a primary predator.Probable previous hybridization between C. latransand C. nigeris dis- cussed.

INTRODUCTION Two species of wild canines, red wolves, (Canis niger) and coyotes (C. latrans) have been reportedin recentyears fromArkansas (Sea- lander, 1956), Louisiana (Lowery, 1943), eastern Oklahoma (Blair, 1939; McCarley, 1952) and eastern Texas (McCarley, 1959). Both species, as presently defined, show a considerable amount of geographic variation and morphological overlap of both skeletal and pelage characteristics.Considerable confusion exists in speciesidentifi- cation in areas where bothmay occur. This paper is an analysis of the relationshipthat currentlyexists between coyotesand red wolves in the south central United States (Arkansas, Louisiana, Oklahoma and Texas) based largelyon skull morphology. The study of variation in red wolves by Young and Goldman (1944), resulted in the naming of three subspecies of red wolves, largely on the basis of size. The largest of the subspecies,Canis n. niger (Bartram) has a geographicrange in the southeasternUnited States east of the Mississippi River. This formis now presumedto be extinct and, because its range is beyond the confinesof the present study, will not be consideredfurther. The smallest of the red wolf populations was assigned to the subspecies C. n. rufus Audubon and Bachman with a geographicrange in centralTexas, centralOklahoma and northwesternArkansas. A formdescribed as C. n. gregoryiGold- man has been characterizedas intermediatein size betweenniger and rufusand has a geographicrange betweenthat of nigerand rufus,i.e., the area eastwardfrom eastern Oklahoma and Texas to,the Mississippi River and thence northwardinto Illinois and Indiana. Thus a west to east cline ofincrease in size is apparent.

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions Only one recognizedform of coyote (Canis latrans frustrorWood house) has been recordedfrom the geographicarea under consideration (Young and Jackson, 1951; Hall and Kelson, 1959). This, the largestof the coyoteforms, has a range generallysympatric with C. n. rufusand overlaps the range of C. n. gregoryinear the easternborders of Oklahoma and Texas. The two species under consideration are morphologicallyquite similar and have been distinguishedlargely on the basis of size. This similarityof size is particularlytrue of Canis n. rufusand C. 1. frustror. Young and Goldman (1944) stated the problem well: "There appear to be no . . . dependable charactersdistinguishing in all cases small specimens of rufus fromlarge ones of the coyote." At various times workersin canid taxonomyhave proposedcharacters or combi- nations of charactersof reputed value in separatingthe two forms, e.g., skull size (Young and Goldman, 1944), size of canines and spac- ing of premolars (Young and Jackson,1951), index of ratio of palatal width and upper molar tooth row (Howard, 1949), and hind foot length (Hall and Kelson, 1959). All of these criteriawere testedusing skullsand/or specimens of animals previouslyidentified as one species or the other.With the exceptionof overall skull size, all these criteria produced results so inconsistentthat they had little value in distin- guishingC. n. rufusand C. latransfrustror. The problemof separatingC. 1. frustrorfrom C. n. rufusis further complicated by the situation regardingthe holotypes.The holotype of frustroris a young male (about fourmonths old) and includes the skin only. No type specimen has been designatedfor rufusalthough Goldman (1937) restrictedthe name to canid populationsoccurring 15 miles westof Austin, Texas.

METHODS One hundred and seventeenadult skulls of recentorigin (since ap- proximately 1948) were examined and measured. The following measurementswere made of each skull: (1) greatestlength of skull, (2) condylobasal length, (3) zygomaticbreadth, (4) squamosal con- striction,(5) width of rostrum,(6) interorbitalbreadth, (7) length of maxillary toothrow, (8) upper carnassial length, (9) lower carnassial length,(10) space between2nd and 3rd upper premolars,and (11) space between2nd and 3rd lowerpremolars. In addition to the skulls mentionedabove, 17 skulls of C. n. rufus and 8 skulls of C. n. gregoryithat were used by Goldman (Young and Goldmnan,1944) forhis monographof the species were examined,re-

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions measured, and used for subjective comparisons. Two hundred and twenty-oneadditional skulls and/or carcasses of coyotes were examined, but not measured. Examination of the latter specimenswas possible because of the practiceof trappersand otherpredator control workersof hanging the carcasses of killed animals on fence posts by the sides of highwaysthroughout eastern Oklahoma and Texas. When these carcasses were noted they were usually examined on the spot, and unless there was some individual, or some skull, of which the species identitywas in doubt, the carcasses were left as found. This selectivitybiased the data derived fromthe 117 measured skulls in favorof the largerskulls.

DATA

Analysis of all measurementsshowed thatthere was a gradationin size fromthe smallest to the largest skulls of presumed specimensof niger and latrans. On the basis of size, the largestskulls were assignable to C. n. gregoryi.The smallest skulls were obviously assignable to C. latransfrustror. A considerablenumber of skulls,however, were intermediatein size and not easily assignable to eitherspecies. Identi- ficationof these intermediatesized skulls constitutedthe main problem of this study. The majority of the skulls examined were of un- known sex. Consequently,it was necessaryto treatboth sexes together with full recognitionthat males generallyexceeded femalesin size in both species. For convenience,and to have an adequate series in each case to analyze statistically,skulls from several differentlocalities were groupedtogether. Due considerationin thosegroupings was given not only to geographic distribution,but also to ecologic distribution mainly on the basis ofbiotic districts. Figures 1 and 2 representan approach (Hubbs and Hubbs, 1953) to the problem of distinguishingred wolves and coyotes using skull lengthand zygomaticbreadth as indicatorsof size. The measurements used forCanis n. gregoryiand C. n. rufuswere taken fromthe meas- urementsof Young and Goldman (1944) unless otherwisenoted. It can be seen thatthere was a markedsimilarity in relationshipfor both characters for each of the populations from differentareas. (The majority of the skulls from Atoka County, Oklahoma, had broken zygomata and were not included in Figure 2.) The patternexhibited in Figures 1 and 2 was also true of all othercranial featuresstudied. Because skull length and zygomaticbreadth were the best indicators of size, comparisonof these two characterswas deemed the most sig- nificantfor distinguishing coyotes and wolves.

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions Length of Sku IllI(mm.) 18 200 220 240 C. n. gregoryl(50)

Okla.,McCurtain Co. (2)

Louisiana (4)

C. n. rufus (33) Arkansas(2)

Okla., eastern coun les (10)

Texas, eastern counties (19)

Okla., Bryan Co. (I4) -777

Okla., Jefferson C . (38)

Okla., Okfuskee Co. 1I0)

Ark.,western counties (7)

Okla, Atoka Co. (11) I I I_ _

Fig. 1. Variation of total length of skull of populations of wild Canis fromthe southeastern United States. For each locality the range of variation is shown by a heavy horizontal line: the mean by a small narrow vertical line. The blackened part of each bar comprises two standard errors of the mean on either side of the mean and indicate reliability. One-half of each black bar plus the white bar at either end outline one standard deviation on either side of mean (Hubbs and Hubbs, 1953).

There was a statisticaldifference (a differenceexceeding two standard errorsof the means of two samples was consideredto indicate a differenceof statistical reliability) in skull length and zygomatic breadthbetween skulls identifiedas C. n. gregoryiand all otherpopu- lations identifiedas C. n. rufus and C. 1. frustror,at least as the C. niger populations existed from about 1900 to 1925, which was the inclusive dates on most of the skulls utilized by Goldman and used in this study to establish the range of variation for each subspecies of red wolf. Using the criteriaof skull lengthand zygomaticbreadth, one badly broken and four complete skulls from LaSalle, Madison, and Terre- bonne Parishes, Louisiana (L.S.U. Museum of Zoology) collected from 1935 to 1957, and two skulls from McCurtain County, Okla- homa, (Univ. of Ark., Dept. of Zoology) collected in 1936, were ref- erable to C. n. gregoryi (Figures 1 and 2). Using the same criteria, two skulls fromArkansas (Stone County,1936; and localityunknown, 1949), (Univ. of Ark.,Dept. of Zoology), were referableto C. n. rufus (Figures 1 and 2).

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions 90Zygomatic Breadth110 (mm.) 130 C.n. gregoryi (50)

Okla., McCurtain Co.(2)

Louisiana (4)

C. n. rufus C33) I m

Arkansas (2)

Okla., eastern counties(10)

Texas, eastern counties (19)

Okla,, Bryan Co. (14) I '_ ...

Okla., Jefferson Co.(38) 1 I I , Okla., Okfuskee C o. (10) _ i 1 , Ark.,western counties (7) J I

Fig. 2. Variation of zygomatic breadth of skulls of population samples of Canis from the southeastern United States. For explanation see Figure 1.

All skulls fromeastern Texas, southernand central Oklahoma and westernArkansas (other than the two mentionedabove) were refer- able to C. latransfrustror, using the same criteriaas that given above. (The Bryan and JeffersonCounty samples may be consideredas most typical of C. latrans frustror.) Skulls fromthe easterncounties of Oklahoma (Choctaw,McCurtain, Pushmataha, and Latimer counties) collectedsince 1949 were, on the average, larger than skulls collected elsewhere and assigned to C. latrans on the basis of descriptionsof Young and Jackson (1951). The mean length and mean breadth of zygomata,however, were not sig- nificantlydifferent (Figures 1 and 2) fromthe means of skullsof C. n. rufus (so identifiedby Goldman) fromTexas and Oklahoma. In general, however,these recent Oklahoma skulls were smaller and of less massive bone structurethan the 17 skullsof C. n. rufus (collectedfrom 1900 to 1925) used for comparativematerial. The eastern Oklahoma skullswere intermediatein size betweentypical C. 1.frustror and C. n rufus. A subjective comparison of the largest of these eastern Okla- homa skulls with a series of seven near topotypesof C. n. rufus (used by Goldman for the descriptionof rufus) revealed that none of the

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions eastern Oklahoma skulls has massive enough bone structureor other combinationsof charactersthat would justifyassigning them to C. niger. This was emphaticallytrue when the sex of the animal from which the skull came was considered.Known skulls of males from eastern Oklahoma overlapped in size only the female skulls of rufus. On the basis of these observations,it was apparent that none of the easternOklahoma skullswas assignableto C. niger. On the basis of the evidence presentedin Figures 1 and 2, all of the wild Canis currentlyoccurring in Arkansas (except the two skulls assigned to C. n. rufus), Oklahoma and Texas are referableto C. latransfrustror. Admittedly, the available evidencewhich discountscur- rentreports of red wolves fromthese areas is of a negativenature, but it seemslikely that if animals large enoughto be consideredred wolves currentlyexisted in these areas, at least some recentspecimens would have been available. The situationin Louisiana is apparentlysomewhat different. On the basis of actual specimens,C. niger has been collected as recentlyas 1956 and 1957 fromTerrebonne and Madison Parishes, respectively. Apparentlythe species is presently (1961) extant in some of the al- luvial swamps of easternand southernLouisiana.

DISCUSSION

The questionthat should be discussedis: what happened to the population of animals known as Canis niger which, prior to 1935, appar- ently were presentin the south centralUnited States in considerable numbersand apparentlyare notnow present,at least in the abundance of formeryears? The difficultyof suitably answeringthis question is thatit is impossibleto regressin time,and the apparent extirpationof the population known as Canis nigerwas not well documentedeither by reportsor by specimens. One possible answer is based on the premise that the population known as C. n. rufuswas a valid taxon and could be considereda red wolf and not a large race of the coyote.It is interestingto note in older faunal accounts such as Bailey's (1905) publicationthat coyoteswere not recordedfrom the eastern wooded part of Texas, but red wolves [Canis frustror= Canis niger] were presentand fairlycommon. Low- ery (1943) noted that red wolves were decreasingin Louisiana and did not list coyotesas part of the Louisiana fauna at that time. The time of apparent decrease of red wolves in the geographicarea under consideration,particularly in easternTexas and Oklahoma, coincided with intensivelumbering and agriculturalpractices. It is known that

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions coyotepopulations in these areas have increased in recentyears, now being found in areas where they were not recorded40-45 years ago, but where red wolves were recorded (Bailey, 1905; McCarley, 1959, for example). It could be suggestedthat red wolves were not able to adapt to the man-wroughtenvironmental changes associated with in- tensivefarming and lumberingoperations, and gradually disappeared. Coyotes,on the other hand, have apparentlybeen able to utilize the changinghabitat and have ecologicallyreplaced red wolves as primary predators. A second possible answer is based on the premise that Canis niger rufus was not a valid taxon, but representedthe result of natural hybridizationbetween Canis latrans and Canis nigergregoryi. Young and Goldman (1944) and Young and Jackson (1951) both suggested the possibilityof such hybridizationbetween coyotesand wolves. Support for this hypothesisis available from several sources. A seriesof eightskulls fromthe vicinityof Llano, Texas, assembled and examined by Goldman were re-examined in the present study. At least two of these skulls (U.S.N.M. Nos. 224185 and 228069) were in- distinguishablefrom the majority of larger presumed coyote skulls fromeastern Oklahoma. It is known that coyotesand dogs may cross and produce fertileoffspring (see particularlyGier, 1957, for com- ments on this and additional supportingcitations). McCarley (1959) reportedthe occurrenceof two siblingdog-coyote natural hybridsfrom eastern Texas. Because of the close relationshipof Canis familiaris, Canis latrans,and Canis niger,coyote-red wolf hybridizationwas en- tirely within the realm of probability,particularly if the environ- mental changes mentionedearlier resulted in a closer contactbetween the two species, i.e., a breakdownof reproductiveisolation. Examination of Figures 1 and 2 show that from a morphological standpointthe population sample of C. n. rufus,as it existed priorto 1925, was morphologicallydistinct from C. n. gregoryiat least in the non-overlapof standarderrors of means. This same populationsample of C. n. rufus was not, however, statisticallydifferent on the basis of skull size (Figures 1 and 2) frompresent population samples from eastern Oklahoma which have characteristicswithin the range de- scribedfor C. latransfrustror (Young and Jackson,1951). In addition there is a fairlyregular cline of increase in size fromwest to east of these present-daycanid populationsin Oklahoma and Texas. It seems plausible to hypothesizethat sometimein the past (prior to 1900) interspecifichybridization between coyotes and red wolves (probably C. n. gregoryi),occurred. This hybridizationprobably oc- curredfirst in centralOklahoma and Texas as Goldman suggested,pro-

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions ducing a hybridpopulation describedas C. niger rufus.As the coyote populations continued to expand eastward, hybridizationincreased, gradually swamping out the red wolf populations as the previously effectiveisolation mechanisms (geographic,ecological?) broke down. The population sample of recent Canis with the largest skull dimen- sions came fromthe eastern counties of Oklahoma, presumably the last portionof Oklahoma to be extensivelyinfluenced by the activities ofman. The skullsfrom eastern Oklahoma were,on the average,larger than typicalcoyotes, yet considerablysmaller than C. n. gregoryi.This suggeststhat the populationsof Canis in easternOklahoma may pres- entlybe of hybridcharacter. It may also be of significanceto note that as far as is known,no coyotesoccur in Louisiana in contactwith the apparent extantpopulations of red wolves, (Geo. H. Lowery, Jr.,per- sonal communication,1961.)

SUMMARY Samples of skulls of wild Canis populationsfrom Arkansas, Louisi- ana, Oklahoma and Texas were examined,measured and analyzed in an attemptto distinguishskulls of coyotes (Canis latrans) fromskulls of red wolves (Canis niger). It was foundthat, in general,size of skull was the mostreliable characterfor separating the two species. On the basis of totallength of skull and zygomaticbreadth, the followingcon- clusionswere reached: At present(1961), Canis nigeris extantonly in a few places in eastern and southernLouisiana. All currentpopula- tion samples of Canis in Arkansas, Oklahoma, and Texas that were examined were referableto Canis latransfrustror on the basis of skull size. It was hypothesizedthat the apparent extirpationof red wolves in these latter states was the result of (1) non-adaptabilityof red wolves to changing environmentalconditions, including competition with coyote populations, and (2) probable hybridizationbetween coyotes and red wolves, resultingin the blending of red wolf and coyotecharacters into a formknown as Canis niger rufus.It was suggestedthat C. niger rufuswas not a valid taxonomicentity, but rather a populationof natural hybridsbetween C. latrans and C. nigergregoryi. ACKNOWLEDGMENTS Appreciation is expressed to Bryan P. Glass, George H. Lowery, Jr.,Richard A. Manville, RobertPackard and JohnA. Sealander for permissionto examine skulls in theircare. Fred Rainwater did many of the skull measurements.At various times the problem has been

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This content downloaded from 128.192.114.19 on Fri, 24 May 2013 18:39:43 PM All use subject to JSTOR Terms and Conditions discussedwith various workers. Thanks are particularlydue W. F. Blair,W. B. Davis,H. T. Gier,Bryan P. Glassand O'RileySandoz for theircomments, criticism, and advice.M. D. Bryantkindly read the manuscript.

LITERATURE CITED

BAILEY, VERNON. 1905. Biological Survey of Texas. North Amer. Fauna, 25: 1-222. BLAIR, W. F. 1939. Faunal relationshipsand geographic distributionof mammals in Oklahoma. Amer. Midl. Nat., 22: 85-133. GIER, H. T. 1957. Coyotes in Kansas. Agric. Exp. Sta., Kans. St. Coll. of Agric. and App. Sci. Manhattan, Bull. 393: 1-96. GOLDMAN, E. A. 1937. The wolves of North America. Jour.Mamm., 18: 37-45. HALL, E. R., and KEITH R .KELSON. 1959. The Mammals of North America. The Ronald Press, New York, 2: 547-1083. HOWARD, WALTER E. 1949. A means to distinguish skulls of coyotes and domesticdogs. Jour. Mamm., 30: 169-171. HUBBS, CARL L., and CLARK HUBBS. 1953. An improved graphic analysis and comparisonof series of samples. Syst. Zool., 2: 49-57. LOWERY, GEO. A., JR. 1943. Check-listof the mammals of Louisiana and ad- jacent waters. Occ. Pap., Mus. Zool., St. Louis Univ., 13: 213-257. McCARLEY, HOWARD. 1952. The ecological relationships of the mammals of Bryan County,Oklahoma. Tex. J. Sci., 4: 102-112. . 1959. The mammals of eastern Texas. Tex. Jour. Sci. 11: 385-426. SEALANDER, JOHN A. 1956. A provisional check-listand key to the mammals of Arkansas (with annotations). Amer. Midl. Nat., 56: 257-296. YOUNG, S. P., and E. A. GOLDMAN. 1944. The wolves of North America. Amer. Wildl. Inst., Washington, Part II: 389-588. YOUNG, S. P., and H. H. T. JACKSON. 1951. The clever coyote. Stackpole Co. and Amer. Wildl. Inst., Washington, Part II: 229-411.

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