Geographic Variation in the Pocket Gopher, Thomomys bottae, in Colorado

by Phillip M. Youngman

SUMMARY

A study of 249 specimens of Thomomys bottae from Colorado reveals six subspecies in the state. T. b. aureus and T. b. howelli occupy the Colorado Plateau Region in the western and southwestern parts of the state. T. b. internatus, T. b. cultellus, T. b. pervagus, and the newly named T. b. rubidus occupy part of the Southern Rocky Mountain Region and a narrow strip of the Great Plains.

The greatest amount of geographic variation, in Thomomys bottae in Colorado, occurs in the ecotone between the grassland and coniferous forest at the edge of the Great Plains, and in the ecotone between the Piñon, juniper, and sage of the Colorado Plateau and the Coniferous forest of the southern Rocky mountains.

Table 1. Measurements, in Millimeters, of Thomomys bottae

Unless otherwise noted, specimens are adults from Colorado

Sex	Catalog number or number of individuals averaged	Total length	Tail	Hind foot	Condylobasal length	Nasal length	Zygomatic breadth	Squamosal breadth	Length of rostrum	Breadth of rostrum	Alveolar length of upper max. tooth-row	Least interorbital breadth
		Thomomys bottae howelli, holotype
♀	75684[1] [sad.]	219	71	29	37.3	11.1	23.7	20.0	14.5	8.5	7.7	6.6
		Thomomys bottae aureus, Bedrock
♀	2982[2]	217	59	31	40.4	13.8	24.3	20.6	16.7	8.6	9.2	6.8
♀	3013[2]	210	60	29	38.7	13.0	24.4	20.4	15.7	8.1	8.9	7.0
♂	2997[2]	242	73	33	44.7	15.4	28.4	22.8	15.7	10.1	9.0	7.2
		Coventry
♀	6 av.	222	61	31	39.0	12.1	25.4	20.3	15.2	7.8	8.2	6.8
	Max.	229	63	33	40.0	12.8	25.8	20.6	15.6	8.2	8.5	7.0
	Min.	217	58	30	38.3	11.4	25.0	19.3	14.7	7.5	8.0	6.6
♂	3 av.	259	70	35	46.5	15.0	29.3	22.7	17.8	9.2	9 5	6.7
	Max.	270	76	36	48.3	16.0	31.9	23.7	18.0	9.3	9.6	6.9
	Min.	250	65	35	45.5	14.4	27.6	22.2	17.6	9.2	8.0	6.4
		Ashbaugh's Ranch and 15 mi. W Cortez
♀	7 av.	225	67	28	39.0	13.7	24.4	20.2	16.1	8.0	8.3	6.3
	Max.	238	75	31	40.6	14.7	25.0	20.7	16.5	8.5	8.7	6.8
	Min.	216	55	26	37.8	12.9	23.6	19.7	15.5	7.8	7.9	6.1
♂	4 av.	247	73	31	44.2	15.9	27.7	22.1	18.6	9.2	8.4	6.4
	Max.	252	80	34	45.2	16.7	28.8	22.3	19.8	9.6	8.8	6.7
	Min.	244	67	30	43.7	15.5	27.0	21.7	18.0	8.8	8.0	6.2
		Cortez
♀	5120[3]	224	56	28	38.1	12.3	....	19.5	15.4	7.5	7.6	6.5
	5121[3]	220	68	31	38.3	11.6	24.2	19.6	15.1	7.6	8.0	6.7
♂	5124[3]	257	81	33	44.4	15.4	29.5	22.2	18.6	8.9	8.6	6.5
♂	5119[3]	215	62	28	42.0	14.0	27.9	22.1	17.9	8.2	8.6	6.4
		Mesa Verde (combined)
♀	5 av.	221	63	30	39.0	12.6	24.7	20.2	16.0	8.0	8.2	6.7
	Max.	235	66	32	40.4	13.7	25.6	21.1	17.3	8.7	8.5	7.1
	Min.	212	61	28	38.1	12.0	24.1	19.5	15.0	7.7	7.9	6.4
♂	3 av.	246	74	32	43.7	14.9	27.8	22.3	18.3	8.8	8.9	6.6
	Max.	252	79	33	45.0	15.2	28.4	23.0	18.5	9.0	9.0	6.8
	Min.	238	69	31	42.0	14.7	27.5	21.2	18.2	8.7	8.9	6.3
		1 mi. N La Plata
♂	72966[4]	236	70	31	45.4	15.6	29.4	23.3	20.2	8.8	8.5	6.5
		3 mi. W Durango
♀	3 av.	225	65	28	40.1	13.1	25.7	21.0	16.6	8.1	8.3	6.5
	Max.	230	67	29	40.4	13.5	25.8	21.2	16.8	8.4	8.5	6.6
	Min.	219	63	28	39.9	13.0	25.7	20.6	16.5	8.4	8.1	6.4
♂	70054[4]	262	87	35	45.0	15.6	27.9	22.7	19.7	9.3	9.8	6.4
♂	70055[4]	248	79	31	43.3	14.0	27.6	22.1	17.1	8.7	8.2	6.2
		12 mi. W Pagosa Springs
♀	72971[4]	217	65	27	39.1	12.8	....	20.0	15.4	7.4	8.7	6.2
♂	72970[4]	238	70	29	42.7	15.0	27.5	21.8	17.2	8.8	8.3	6.5
		Thomomys bottae pervagus, Antonito
♀	133668[1] [sad.]	208	69	29	37.3	12.9	23.1	18.2	15.8	7.5	8.0	6.9
		Espanola, New Mexico
♀	133616[1]	249	82	38	41.1	....	24.6	20.0	16.3	8.2	8.1	7.1
♀	133619[1]	216	65	32	40.6	....	24.9	19.3	....	8.0	8.0	6.8
♂	58293[1]	244	76	31	44.0	16.1	26.9	21.2	18.3	8.8	8.1	6.6
		Thomomys bottae internatus, Salida
♀	11 av.	219	67	31	38.6	13.4	23.2	19.5	15.4	7.6	7.8	6.5
	Max.	242	80	34	40.4	14.2	25.0	20.2	16.2	8.1	8.4	6.9
	Min.	196	45	29	37.6	12.9	21.9	18.8	14.8	7.3	7.0	6.3
♂	3 av.	247	74	32	42.9	16.1	25.1	20.9	18.0	8.2	8.0	6.3
	Max.	248	74	33	43.7	16.3	26.4	21.7	18.1	8.8	8.1	6.4
	Min.	247	74	32	42.2	15.9	25.8	20.5	17.9	7.9	7.9	6.3
		12 mi. N Cañon City
♀	72945[4]	230	81	28	38.1	13.0	22.6	19.4	15.0	7.9	8.0	6.7
♀	72947[4]	228	74	27	38.7	14.0	23.6	19.8	15.9	8.2	8.1	6.8
		1 mi. W Coaldale
♀	70042[4]	224	70	30	38.1	13.1	23.5	19.5	15.6	7.7	7.5	6.6
		5 mi. S Cotopaxi
♀	72932[4]	224	65	27	39.1	13.8	24.3	20.4	15.5	7.7	7.5	6.5
♂	72925[4]	250	74	29	44.0	16.2	27.5	22.8	18.7	9.0	8.1	6.1
		9 mi. SSW Colorado Springs
♀	72942[4]	225	77	29	38.8	14.1	23.3	20.2	15.4	7.8	8.3	6.7
	72943[4]	219	70	28	37.7	13.5	23.0	19.7	14.8	7.6	8.4	6.8
		2-1/2 mi. S Wetmore
♂	70053[4]	250	81	30	42.5	16.7	26.3	22.3	17.7	8.5	7.9	5.9
		200 yards E St. Charles River, 8 mi. W Pueblo
♀	73497[4]	226	69	30	39.3	13.9	24.9	20.5	15.7	7.7	7.9	7.2
♀	73498[4]	216	64	29	38.0	12.9	24.2	20.1	15.1	7.7	7.4	6.7
		St. Charles Mesa
♀	4860[3]	222	70	29	38.2	13.5	....	19.3	15.9	8.2	7.5	6.5
♂	4864[3]	240	72	33	43.1	15.8	....	21.4	17.6	9.2	7.9	6.7
		11 mi. WNW Gardner
♀	70052[4]	227	64	28	37.9	13.0	22.5	18.8	14.8	7.3	8.0	6.7
		1-1/2 mi. S Redwing
♀	72940[4]	227	73	28	39.0	13.1	23.1	18.8	15.6	7.8	8.0	6.8
		1 mi. E La Veta
♂	70049[4]	254	88	32	42.4	15.1	27.5	21.8	17.3	8.4	8.2	6.5
♂	70044[4]	239	80	32	42.3	16.5	27.8	22.0	17.9	8.7	8.1	6.4
		Thomomys bottae cultellus, Fishers Peak
♀	129285[1] [sad.]	214	64	27	37.2	13.0	....	19.0	15.3	7.7	7.6	6.5
		Thomomys bottae rubidus, holotype and topotypes
♀	72952[4]	233	80	28	40.6	14.2	25.1	20.8	16.7	8.8	7.5	6.9
♀	72954[4]	225	80	28	40.3	14.2	24.6	20.6	16.6	9.2	7.2	6.9
♂	3 av.	261	89	31	44.7	15.7	27.8	22.6	18.6	10.1	7.4	6.9
	Max.	270	94	32	45.1	15.9	28.1	22.7	18.8	10.4	7.6	7.0
	Min.	255	85	30	44.2	15.5	27.5	22.5	18.5	9.8	7.2	6.8

sad. denotes subadult.

[1] United States National Museum.

[2] E. R. Warren Collection.

[3] Colorado State University.

[4] Museum of Natural History, University of Kansas.

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