Dung Beetle Body Condition: A Tool for Disturbance Evaluation in Contaminated Pastures

Abstract

The use of veterinary medical products and herbicides is a common practice in intensified livestock systems. These compounds affect nontarget organisms that perform important ecosystem functions, such as dung beetles. The assessment of body condition allows us to determine how individuals respond to changes in the environment. However, assessments of how contamination associated with cattle farming affects coprophagous insects such as dung beetles have not been conducted in natural systems. In the present study, we evaluated the effect of ivermectin (an antiparasitic drug) and herbicides on the body condition of 3 species of dung beetles collected in the field: Copris incertus, Euoniticellus intermedius, and Digitonthophagus gazella. We recorded 3 condition indicators (body size, lipid mass, and muscle mass) of beetles collected from 19 livestock ranches in northeastern Mexico. In general, the use of ivermectin had adverse effects on C. incertus and E. intermedius whereas the effects were positive for D. gazella. Conversely, the use of herbicides had adverse effects on D. gazella and positive effects on C. incertus. The different effects of ivermectin and herbicides found in males and females show that sex can be important in determining individual responses to environmental contamination. Importantly, we provide the first evidence under natural conditions that native and exotic species of dung beetles are highly sensitive to different types of livestock management, with veterinary medications and herbicides having the ability to alter body condition. Changes in dung beetle condition can reduce the ecosystem services that dung beetles provide in livestock systems. Environ Toxicol Chem 2019;38:2392–2404. © 2019 SETAC

Contamination effects on sexual selection in wild dung beetles

“…Notably, in our studied beetles the use of herbicides (in E. intermedius) and ivermectin (in D. gazella) in cattle pastures decreased the magnitude of SSD mainly due to changes female body size, revealing higher plasticity in this sex (Villada-Bedoya et al, 2019).…”

“…For example, in populations of Sepsis punctum and S. neocynipsea (Diptera: Sepsidae), where males are the larger sex, SSD may be absent in stressful environments but may increase as the quality of the environment increases (Rohner et al, 2018). Notably, in our studied beetles the use of herbicides (in E. intermedius ) and ivermectin (in D. gazella ) in cattle pastures decreased the magnitude of SSD mainly due to changes female body size, revealing higher plasticity in this sex (Villada‐Bedoya et al, 2019). This has been reported in many species of insects, where female size appeared to be more plastic than male size, mainly in species with female‐biased SSD (Teder & Tammaru, 2005).…”

“…In general terms, the use of chemical compounds in pastures can affect various parameters related to the individual condition and viability of dung beetle populations (González‐Tokman, Martínez‐Morales et al, 2017; Verdú et al, 2015; Villada‐Bedoya et al, 2019). Under field conditions, both substances have been reported to have species‐ and sex‐dependent effects on body size and physiological condition in dung beetles: in C .…”

“…In E . intermedius , body size and energetic condition decrease with ivermectin use regardless of sex and herbicide contamination (Villada‐Bedoya et al, 2019).…”

“…In general terms, the use of chemical compounds in pastures can affect various parameters related to the individual condition and viability of dung beetle populations (González-Tokman, Martínez-Morales et al, 2017;Verdú et al, 2015;Villada-Bedoya et al, 2019).…”