Digitonthophagus gazella (Fabricius, 1787)

Ivie, Michael A. & Philips, Keith, 2008, Three new species of Canthonella Chapin from Hispaniola, with new records and Nomenclatural changes for West Indian dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 1701, pp. 1-14 : 10-11

Digitonthophagus gazella (Fabricius, 1787)

This African native (sometimes known as Onthophagus gazella ) has been widely introduced to the US mainland in an attempt to control dung flies and helminth parasites, and improve dung incorporation ( Fincher et al. 1983). Since that time, it has proven to be highly mobile and invasive. From initial releases in Texas in 1972, this species has become established from Florida, Georgia, and Missouri to California ( Fincher et al. 1983, Vulinec & Eudy 1993, MacRae & Pen 2001), and has invaded Mexico, Guatemala and Nicaragua, as well as the western Caribbean island of San Andrés ( Rivera-Cervantes & Garcia-Real 1991, Montes de Oca 2001, Noriega & Jorge 2002). It is also present in South America, where it was introduced in the 1980s ( Aidar et al. 2000).

The documentation of this species in the West Indies is very weak. Chalumeau (1983) did not record this species from the French Antilles, but in the only published record from the West Indies it had reached the Windward Island of Martinique by 1992 ( Huchet 1992). We have discovered that this species is present on several islands of the Greater Antilles ( Jamaica, Hispaniola, Puerto Rico, and St. Croix), as well as the Leeward Islands of St. Kitts, Montserrat, and Guadeloupe. Although it was not recorded from Grenada by Woodruff et al. (1998), it is probably now widely distributed on islands with cattle..

The earliest West Indian populations of D. gazella known to us were discovered in the Dominican Republic at 4 km W. Oviedo, 28 November 1990 - 04 February 1991, in flight intercept traps placed in arid thorn forest by L. Manser and S. Peck (CMNC). Later that year, it was taken on the north coast of Jamaica at St. Ann's, 2 mi. E. Discovery Bay, Runaway Caves, 25 March-01 April 1991 by T. K. Philips and L. Gerofsky (TKPC). The next year, specimens were collected in widely distributed areas of the Dominican Republic, at Prov. San Pedro de Macoris, Estacion de Acuacultura, 13 April 1992 (MNHD), at Prov. La Altagracia, Parque Nacional del Este, Boca de Yuma on 30 April by K. A. Guerrero and F. Del Monte (MNHD), and at Prov. Altagracia, 2 km N. Bayahibe, 3 July 1992 (CMNH). Further early Hispaniolan records include Prov. Pedernales, Cabo Rojo to 9.5 km N of Cabo Rojo 5–42m, 8–10 July 1993 (WIBF); Prov. Independencia, S. Lago Enriquillo, 12 July 1993 (WIBF); and Prov. San Juan, 11 km SE Ingenio, Presa de Sabaneta, nr. shore, 19.021N, 71.181W, 31 August 1995 (CMNH).

By 1996, D. gazella had reached Puerto Rico and St. Croix, as documented by Cruzian records from 4 km S. Fredriksted, at black light on 13 February 1996, W.E. Steiner and J. M. Sweringen, and 4 km NW Christiansted on 0 8 February 1996 (NMNH, WIBF). The earliest known Puerto Rican specimen is from Aricebo, vac. Cueva Vaca, 0 4 April 1996 collected by L. A. Barley, in dung (URPB).

The earliest Lesser Antillean specimens of D. gazella we have seen are from Marie-Gallant, taken in August 1992 (FC-INRA). Five months later it was found on the neighboring island of Basse-Terre, taken at Montebello 10 JAN 1992 by Dubois (FC-INRA). Later, F. Chalumeau collected D. gazella on Basseterre at St. Rose, Sofaia, in October 1996 (WIBF). On Montserrat it was common by 24 June 2000 in cow dung on the north end of the island, at least as far south as the Lower Belham River and Isles Bay (WIBF). In 2003, it was found in cow pats on St. Kitts at St. Peter Basseterre Parish, Bayfor’s, 0 2 JULY July 2003 (WIBF). A partial specimen was found on Anguilla under a rotten log in a cow pasture at Low Ground on 17 May 2004 (WIBF).

Thus this species is now on at least nine West Indian islands, with more undiscovered populations probable. Because D. gazella has been implicated in the decline of native species in Texas ( Howden & Scholtz 1986), this particular introduction comes as a very real threat to the native West Indian dung beetles we are just beginning to document. On Hispaniola, Canthon violaceus (Oliver) and C. signifer Harold were common in open areas before the arrival of D. gazella , but may already be reduced in numbers or extirpated from areas now occupied by D. gazella . Both native species were seen by the hundreds in Prov. Pedernales in 1988 (Ivie, Philips, and Johnson expedition), as was C. violaceus in Prov. Independencia in 1991 (Rawlins expedition) and 1992 (Ivie and Ivie expedition). Neither species has been found in those areas in our visits subsequent to the establishment of D. gazella , and only once has either has been found elsewhere after D. gazella is present — 8 specimens of C. violaceus were taken with the 1992 Bayahibe collection (CMNH). It would be a further sad comment on the decreasing richness of the world's biodiversity if these two beautiful scarabs were pushed out by another of man's weedy tag-alongs.

Jamaica also has large endemic species that could be harmed by this introduction, most importantly the pasture-dwelling Sulcophanaeus carnifex (Linnaeus) , Pseudocanthon jamaicenesis Matthews , and even possibly the forest-endemic Jamaican genus Anoplodrepanus , including A. reconditus (Matthews) and A. pecki (Howden) . We have no data to indicate if impacts have occurred, but encourage others with access to such data to make them known as soon as possible.

Matthews' (1966) key to the West Indian genera does not include Digitophophagus gazella , but it cannot be confused with any of the West Indian species illustrated by him. Huchet (1992) gave diagnoses for both the genus and species.