Male flour beetles increase their courtship effort and their sperm count if a female smells of other males according to a study published in the journal Behavioural Ecology.
Researchers from the University of Exeter found that males can detect chemical cues on females that have been in contact with other males and that they use these 'smells' to assess the risk of sperm competition.
If a female has been in contact with fewer than three suitors, males up their game and increase their courtship efforts in order to win her over. However they quickly give up if she smells of more than three rival males.
The researchers also found that males increase their sperm count when mating with females that carry the scent of any other males.
Sarah Lane from the University of Exeter said: "Remarkably, we discovered that although male beetles appear to be willing to take on one or two rivals, they seem to know it is not worth their while to compete with more than three other males. This shows that they are sensitive to indicators of sperm competition, even if the female hasn't actually mated."
Flour beetles exhibit a highly tactile form of courtship in which the male mounts the female and stimulates her, drumming his lower leg along her abdomen until she allows him to mate with her. Such courtship can last for over ten minutes, providing an opportunity for the male to assess the likely sperm competition.
The researchers exposed unmated females to males in a vibrating tube which transferred scent but did not allow them to mate.
The beetles were then observed during courtship to determine whether the number of different male scents on the females influenced courtship effort.
To determine changes in sperm count, females were frozen after mating and the sperm were removed from the reproductive tract and counted.
The scent cues did not provide males with information about female mating status, but rather equipped males with information on the presence and perhaps density of rivals within their mating environment; this information alone elicited an increase in reproductive investment.
The study was carried out in collaboration with Okayama University, Japan.
The research was funded by the Natural Environment Research Council, the Royal Society and the Leverhulme Trust.
About the University of Exeter
The University of Exeter is a Russell Group university and in the top one percent of institutions globally. It combines world-class research with very high levels of student satisfaction. Exeter has over 19,000 students and is ranked 7th in The Times and The Sunday Times Good University Guide league table, 10th in The Complete University Guide and 12th in the Guardian University Guide 2014. In the 2014 Research Excellence Framework (REF), the University ranked 16th nationally, with 98% of its research rated as being of international quality. Exeter was The Sunday Times University of the Year 2012-13.
The University has four campuses. The Streatham and St Luke's campuses are in Exeter and there are two campuses in Cornwall, Penryn and Truro. The 2014-2015 academic year marks the 10-year anniversary of the two Cornwall campuses. In a pioneering arrangement in the UK, the Penryn Campus is jointly owned and managed with Falmouth University. At the campus, University of Exeter students can study programmes in the following areas: Animal Behaviour, Conservation Biology and Ecology, English, Environmental Science, Evolutionary Biology, Geography, Geology, History, Human Sciences, Marine Biology, Mining and Minerals Engineering, Politics and International Relations, Renewable Energy and Zoology.
The University has invested strategically to deliver more than £350 million worth of new facilities across its campuses in the past few years; including landmark new student services centres - the Forum in Exeter and The Exchange at Penryn - together with world-class new facilities for Biosciences, the Business School, the Centre for Ecology and Conservation and the Environment and Sustainability Institute. There are plans for another £330 million of investment between now and 2016.
About the University of Exeter's Centre for Ecology and Conservation (CEC)
Staff at the Centre for Ecology and Conservation, based on the Penryn Campus, undertake cutting-edge research that focusses on whole organism biology. The CEC has three interlinked research groups: Behaviour, Ecology and Conservation, and Evolution which constitute 40 academics and over 100 early career researchers. It engages widely with businesses, charities and government agencies and organisations in Cornwall, the Isles of Scilly and beyond to translate its research into societal impact. Staff at the CEC deliver educational programs to some 500 undergraduate and 100 postgraduate students.
A new £5.5 million Science and Engineering Research Support Facility (SERSF) is currently under construction at the Penryn Campus. The facility will bring pioneering business, science and engineering together and will provide space for the growing CEC alongside the University of Exeter Business School, which is expanding into Cornwall, and the University's Marine Renewables team.
The University of Exeter and Falmouth University are founding partners in the Combined Universities in Cornwall (CUC), a unique collaboration between six universities and colleges to promote regional economic regeneration through Higher Education, funded mainly by the European Union (Objective One and Convergence), the South West Regional Development Agency and the Higher Education Funding Council for England, with support from Cornwall Council.