Evaluation of pocket gopher diet in a perennial productive area

Abstract

The desert pocket gopher (Geomys arenarius) is a fossorial herbivorous rodent of the family Geomyidae. Its distribution range is restricted to New Mexico and Texas, in the United States of America, and northern Chihuahua, in México. The Médanos de Samalayuca Flora and Fauna Protection Area (MSFFPA) is located in northern Chihuahua. Different economic activities are carried out in this region, mainly irrigated crops of pecans (Carya illinoinensis). Populations of G. arenarius have been recorded within these areas. Therefore, the objective of this work was to define the extent of the trophic niche and the changes in the physical condition of G. arenarius in a ranch within the MSFFPA over three contrasting seasons (dry, wet, and post-wet). Forty G. arenarius specimens were collected from Arantxa Ranch. Morphometric measurements and the weight of collected individuals were recorded, and the digestive tract was removed to prepare histological slides. Seven 25 m²-quadrants were established, and the species of the vegetation cover were recorded and collected for reference. The Seasonal Fitness Index (IK) and Levin’s Niche Breadth Index were calculated. Males had higher average measurements and weight than females. The IK was 2.82 ± 0.47 in males and 2.64 ± 0.61 in females. Significant differences in the IK between seasons were only found in females. The correlation between IK and plant cover was strong for males and females. The diet mainly comprised Physalis hederifolia, Dimorphocarpa wislizeni, and Cenchrus incertus. Levin’s index showed that G. arenarius is a specialist rodent. Sexual dimorphism was evident, with males larger than females. The physical condition index of gophers is influenced by resource availability. In other studies, this parameter has been related to changes in food availability. It has been reported that gophers tend to feed mainly on crops; however, pecan cultivation was not a major element in the diet of the desert pocket gopher, as it feeds on the vegetation associated with crops. Gophers are considered generalists; nonetheless, the present study showed that G. arenarius is a specialist, although this may be a consequence of anthropogenic activities.

Population genetic structure of a Chihuahuan Desert endemic mammal, the desert pocket gopher,Geomys arenarius

“…Density, in turn, is likely impacted by food availability which has been shown for G . arenarius in the vicinity of Samalayuca dune fields to include both monocots and dicots in 10 plant families (Rueda‐Torres et al, 2022 ) and in the closely related species G . bursarius and G .…”

“…Differences in population size could be caused by differences in the size of a habitable area or population density. Density, in turn, is likely impacted by food availability which has been shown for G. arenarius in the vicinity of Samalayuca dune fields to include both monocots and dicots in 10 plant families (Rueda-Torres et al, 2022) and in the closely related species G. bursarius and G. attwateri to be primarily grasses and to a lesser extent forbs (Luce et al, 1980;Myers & Vaughan, 1965;Williams & Cameron, 1986). Little is known about the abundance of G. arenarius within Socorro Co., as they have been documented infrequently within this area, but based on our own observations, G. arenarius is abundant in the vicinity of White Sands.…”

“…Pocket gophers (Geomyidae) feed mostly from their underground tunnels and are generalist herbivores. Geomys arenarius in Mexico was documented to consume both monocots and dicots in 10 plant families (Rueda-Torres et al, 2022). G. attwateri, a species closely related to G. arenarius, consumed 36 of the 51 plant species available to them (Williams & Cameron, 1986).…”

“…Pocket gophers ( Geomyidae ) feed mostly from their underground tunnels and are generalist herbivores. Geomys arenarius in Mexico was documented to consume both monocots and dicots in 10 plant families (Rueda‐Torres et al, 2022 ). G .…”

Vascular plants of the Médanos de Samalayuca natural protected area, Chihuahua, Mexico

“…Anthropogenic activities and the associated flora.-In some areas, the original plant cover has been replaced by irrigated crops, mainly pecan (Carya illinoinensis), with about 400 ha (Rueda-Torres et al 2022b), as well as vines (Vitis vinifera) and pistachios (Pistacia vera), besides the impact of extensive cattle farming. The area is also a popular recreational destination for ecotourism and adventure tourism, has been the scenery for some movies (Chihuahuan Frontier 2009), and has been considered with potential industrial use (Cruz Sánchez et al 2007).…”