Factors influencing duiker dung decay in north-east Gabon: are dung beetles hiding duikers?

We analysed seasonality of dung decay time and the influence of rainfall, leaf fall, beetle attack and moisture on dung decay. Our study was carried out at the Ipassa Reserve, north-east Gabon. We compared the seasonality of dung decay with the seasonality of dung beetle abundance and guild structure. Dung beetle activity was the main factor influencing dung decay in our study site. Decay time was the highest during the main dry season (3.4 days) and the lowest during the short rainy season (0.7 days). Dung decay time was closely related to dung beetle abundance, especially to the abundance of nocturnal beetles. We discuss the implications of such results for duiker survey methods based on dung pellet counts in areas where decay time is extremely short or unknown

The negative effects of the residues of ivermectin in cattle dung using a sustained-release bolus on Aphodius constans (Duft.) (Coleoptera: Aphodiidae)

This paper reports the findings of two trials into the effects of the treatment of cattle with ivermectin slow-release (SR) bolus on the larval development of the dung beetle Aphodius constans Duft. Rectal faecal samples were collected prior to treatment and every 3 and 2 weeks in a first and second trial, respectively, and up to 156 days post-administration of the SR bolus. Faecal ivermectin concentration reached a peak at 63 days post-treatment (1427 ng$\cdot$g$^{-1}$) and ivermectin was detected up to 147 days post-treatment in the first trial (7.2 ng$\cdot$g$^{-1}$). First stage larvae of A. constans were reared with control or contaminated dung and adult beetles were counted after emergence. In the first trial, the comparison of pairwise samples showed that ivermectin prevented the development of larval A. constans until day 105, while at day 135 the rate of emergence was still significantly lower than the corresponding series of control ($p < 0.05$). In the second trial, the difference between control and treated series remained significant until 143 days post-treatment, with no emergence until 128 days post-administration of SR bolus to cattle. These results show the negative effect of ivermectin on the development of larval A. constans, even at a low concentration (38.4 ng$\cdot$g$^{-1}$). The administration of ivermectin sustained-release bolus to cattle was highly effective in killing dung beetle larvae for approximately 143 days after treatment. The results were similar when dung was obtained from a single animal kept alone, or from a blending of faecal pats obtained from a group of animals kept in field conditions during the whole trial period.Effets négatifs des résidus d'ivermectine délivrés par un bolus à diffusion lente sur la survie du coprophage Aphodius constans (Duft.) (Coleoptera: Aphodiidae). À la suite du traitement de bovins par un bolus à diffusion lente d'ivermectine (12 mg$\cdot$j$^{-1}$), deux expérimentations indépendantes ont été conduites pour en étudier les conséquences sur le développement larvaire du coléoptère coprophage Aphodius constans Duft. Des échantillons de bouse ont été prélevés avant le traitement puis régulièrement, respectivement chaque 3 et 2 semaines pour la première et la seconde expérimentation, ceci jusqu'à 156 jours après l'administration du bolus aux animaux. Les bouses utilisées ont été congelées puis stockées plusieurs mois avant leur utilisation. La concentration fécale d'ivermectine atteint un pic 63 jours après le traitement (1427 ng$\cdot$g$^{-1}$) et l'ivermectine était encore détectable dans la bouse après 147 jours (7.2 ng$\cdot$g$^{-1}$). Des larves d'A. constans ont été nourries avec de la bouse (plusieurs séries, correspondant chacune à une date après traitement) et les imagos obtenus à l'issue du développement larvaire ont été décomptés à l'émergence. Dans la première expérience (animal isolé), la mortalité des larves a été totale jusqu'à 105 jours après le traitement, tandis que 135 jours après l'administration du bolus la bouse contenait encore suffisamment d'ivermectine pour que le taux d'émergence soit significativement inférieur à celui du témoin ($p < 0.05$). Dans la seconde expérience (bouses homogénéisées provenant de plusieurs animaux traités), les différences entre séries bolus et séries témoins restaient significatives jusqu'à 143 jours après le traitement, avec une émergence nulle jusqu'à 128 jours après le traitement. Ces résultats démontrent l'effet négatif de l'ivermectine sur le développement larvaire d'Aphodius constans, même à faible concentration (38.4 ng$\cdot$g$^{-1}$). On peut considérer que l'administration d'un bolus à diffusion lente d'ivermectine a un effet négatif sur les larves de coprophages jusqu'à 143 jours après le traitement. Ces résultats sont similaires si la bouse provient d'animaux isolés ou en mélange

Environmental risk assessment of veterinary pharmaceuticals: Development of a standard laboratory test with the dung beetle Aphodius constans

International audienceThe environmental risk assessment of veterinary pharmaceuticals for dung beetles is required if the substance is an anti-parasiticide for the treatment of pasture animals. However, the demonstration of the environmental safety of those substances for dung fauna is hampered by the fact that no standardized laboratory test system is currently available. Here a test system using the temperate dung beetle species Aphodius (Agrilinus) constans (Scarabaeidae: Aphodiinae) Duftschmidt is described. The survival of first instar larvae of A. constans exposed to a model substance, dimethoate, spiked into formulated (i.e. dried, formulated and re-wetted) or fresh dung was measured over a period of three weeks. Larvae performed better in formulated dung which also proved to be more suitable for mixing-in test substances homogenously. Dimethoate caused significant larval mortality with LC50 values within a range of 1.3–2.8 mg a.s./kg dung (d.w.), depending on the dung type. Based on the data presented here, it is recommended to incorporate this new test system in the risk assessment process for veterinary pharmaceuticals. However, an international ringtest should to be performed beforehand to ensure adequate validation of the method

Fate of ivermectin in soil and impact on micro-organisms

National audienc

Evaluation de l'impact éco-toxicologique résultant de l'usage de médicaments antiparasitaires en élevage extensif

National audienc

Evaluating long‐term ivermectin use and the role of dung beetles in reducing short‐term CH4 and CO2 emissions from livestock faeces: a mesocosm design under Mediterranean conditions

1. Greenhouse gas (GHG) emissions from livestock contribute significantly to global warming, and a reduction of this source of emissions is crucial in achieving the goal of mitigating global warming. 2. CO2 and CH4 emissions from dung pats were analysed by means of a mesocosm experiment in a Mediterranean ecosystem. The experiment consisted of a total of 30 mesocosms distributed across three treatments: a well‐preserved, undisturbed dung beetle assemblage associated with organic livestock; a dung beetle assemblage that was impoverished as a result of the long‐term use of veterinary medical products; and a control treatment without dung beetles. 3. Corrections related to insect respiration allow researchers to provide more precise measurements of CO2 emissions from dung, especially in the initial and final phases of dung exposure, when the percentage of CO2 emitted by dung beetles can become greater than the emissions from the dung pats themselves. 4. The effects of dung beetles on CO2 and CH4 emissions are much more accentuated in warm‐temperate conditions than in northern temperate areas previously studied. Mediterranean assemblages remove and spread dung faster and more effectively than do northern dung beetle assemblages characterised by a lower functional richness and beetle abundance and biomass. 5. From a livestock management viewpoint, mesocosms representing areas with impoverished dung beetle assemblages, due to the long‐term use of veterinary medical products, such as ivermectin, emitted 1.6‐ and 2.8‐fold higher total CO2 and CH4, respectively, than mesocosms mimicking sites with untreated livestock.Financial support was provided by the projects CGL2015-68207-R of the Secretaría de Estado de Investigación, Ministerio de Economía y Competitividad