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Animal Behaviour 80 (2010) 1–2

Contents lists avai

Animal Behaviour

journal homepage: www.elsevier .com/locate/anbehav

In Focus

Featured Articles in This Month’s Animal Behaviour

Figure 1. A hedgehog individually marked with both plastic tubing attached to itsspines and a radiotransmitter. Photo: Les Stocker.

When did the hedgehog cross the road?

For each morning as I travelAnd no short distance that,All I see are hedgehogs,Squashed. And dead. And flat. PamAyres

Flat hedgehogs are a fact of life in Great Britain. In recent years,however, the number of hedgehogs killed on the road in severalrural regions has dropped, suggesting that hedgehog populationsmay be declining. Possible causes include predation by badgers,a greater density of both roads and the amount of traffic on them,increased use of agricultural chemicals and habitat changes causedbymodern agricultural practices. These changes in hedgehog abun-dance further suggest that, nowadays, there may be more hedge-hogs living in urban, rather than agricultural, habitats.

Animals that ‘move’ into urban areas in this way often do verywell because they benefit both from greater food availability,supplied either inadvertently or deliberately by humans, and lowerpredation risk compared to their natural habitat. But life in the BigSmoke has its own drawbacks, as urban areas also carry risks.Hedgehogs remain vulnerable to predation by badgers (a speciesthat also does well in urban habitats), traffic levels remain high insuch areas, and there is also the added risk of disturbance fromhumans and predation by domestic dogs. Studies of badgers andfoxes have revealed how they cope with life in town, but so far,the ways in which hedgehogs trade off the risks and benefits ofan urban lifestyle remain little known, despite their popularity asgarden visitors, and the public’s general affection for them. In thismonth’s issue (pp. 13–21), Claire Dowding and Stephen Harrisfrom the University of Bristol, Simon Poulton of Biological andEcological Statistical Services and Philip Baker of the University ofReading rectify this, reporting on how hedgehogs negotiate theurban landscape of Bristol.

The researchers captured hedgehogs by systematically searchingplaying fields, footpaths, road verges and pavements. They markedthemwithplastic tubingattached to theirdorsal spines so theycouldbe recognized again, and larger hedgehogs also had a radiotransmit-ter attached to them (Fig. 1). In this way, Dowding and colleaguescould track the hedgehogs on foot as theymade their nightly forays,and so map their movement and activity patterns.

As one would predict, the hedgehogs behaved in ways thatincreased their chances of finding food while avoiding danger. Thismeant showing a preference for the back gardens of semidetachedand terraced houses, rather than front gardens (where the risk ofhuman disturbance is higher), and avoiding roads and road verges.Intriguingly, detached houses were preferred by males but avoided

0003-3472/$38.00 2010 The Association for the Study of Animal Behaviour. Published bdoi:10.1016/j.anbehav.2010.05.008

by females. Previousworkon badgers showed that their activitywashigher in gardens with larger lawns and a greater diversity of fruitand vegetable patches: all features more likely to be associatedwith the gardens of detached houses. The researchers suggest thatthis sex difference in hedgehog preference may represent a badgeravoidance strategy on the part of females, who need a safe place toraise offspring. Males, in contrast, appear to be trading off the risksof falling prey to a badger against the gains to bemade from rangingmorewidely and so encounteringmore potential mates. Hedgehogswere also more active after midnight than before, suggesting thatthey may be responding to the marked reduction in human activityduring the small hours of themorning. Thiswas also true evenwhentheweatherwaswarmand hence invertebrate preywere abundant:hedgehogs only took advantage of greater prey availability aftermidnight, again suggesting that avoiding disturbance by humansand their dogs is a major factor influencing their activity.

Finally, Dowding and colleagues were able to show that, despitean aversion to roads themselves, hedgehogs did not actively avoidcrossing roads. Moreover, the rate at which they crossed roads wasnot affected by time of night. Unlike foxes, which tend to crosseven minor roads more frequently after midnight when there ismuch less traffic, hedgehogs were just as likely to cross beforemidnight as after. As hedgehogs were less active before midnight,however, they nevertheless reduced the number of roads crossedduring periods of high traffic, and so reduced their chances ofbecoming road kill. While one might expect to find that foxes and

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In Focus / Animal Behaviour 80 (2010) 1–22

hedgehogs avoid crossing major roads when it is busy, the fact thatbothspeciesavoidcrossingevenquiet residential streets is a surprise.

All thesebehavioural responses suggest that avoiding theparticularrisks presented by an urban environment has a strong influence onhedgehog behaviour, just as it does for foxes and badgers. The capacityto copewith the challenges of human-dominated habitats is obviouslythe key to a successful transition to the town from the country, and itseems clear that the urban hedgehogs of Bristol have found a way toavoid the fate of ending up squashed and dead and flat.

Louise BarrettExecutive Editor

Figure 2. A pair of mating cucumber beetles. Photo: Douglas W. Tallamy.

A Female Preference for Dissimilar Males in an Insect

Females in a variety of vertebrate groups are influenced in theirmating preferences by the immune systems of prospective mates,preferring males that have either particularly effective immunesystems (superior immunocompetence) or immune systems partic-ularly compatible with that of the female (superior immunocom-patibility). Mating patterns in vertebrates from fish to mammalssuggest that immunocompatibility is judged at least inpart on geno-type at the major histocompatibility complex (MHC), which can beassessed externally because MHC affects an individual’s odour aswell as its immune function. In a paper in this issue (pp. 9–12), JaredG. Ali and Douglas W. Tallamy show that females of an invertebratespecies, the spotted cucumber beetle (Fig. 2), also prefer immuno-compatible males and that they may judge males on this trait usingodours generated by cuticular hydrocarbons.

Female spotted cucumber beetles exercise mate preferencesduring rather than before copulation, by choosing whether or notto relax their vaginal duct muscles to allow the male to transfera spermatophore. Ali and Tallamy mated each of a series of femaleswith a different pair of males, and focused on those females thataccepted one male and rejected the other. They then measuredthe cuticular hydrocarbon signatures of their subjects using gaschromatography, and from those signatures produced two metricsof male–female similarity. Males that were accepted by femalesproved to have significantly lower similarity on both metrics thanmales that were rejected. Ali and Tallamy also assessed one aspectof immune response in their male subjects, by implanting themwith short lengths of nylon monofilament, and measuring theproportion of the implant subsequently encapsulated bymelanizedhaemocytes. Accepted males did not perform better than rejectedmales on this measure of immunocompetence.

In a second experiment, Ali and Tallamy forced some females toaccept a male that they had initially rejected; this could be done by

the simple expedient of giving the females no access to other males.Accepted males were again more dissimilar to females in cuticularhydrocarbons than were rejected males. Accepted males also wereagain no more immunocompetent than rejected males in the mela-nization test. Offspring of accepted males, however, showed signif-icantly better performance in the melanization test than theoffspring of initially rejected males.

The results of Ali and Tallamy’s experiments are consistent withthe hypothesis that female cucumber beetles use the odours gener-ated by the cuticular hydrocarbons of males to choose mates whosegenotypes are different from their own. The results further suggestthat females indirectly benefit from this pattern of choice throughobtaining immunocompatible mates and hence generatingoffspring with superior immune systems. This system of femalechoice appears very similar to MHC-based mate choice in verte-brates, except that the MHC genes are known to affect immuneresponse directly, whereas this seems not to be known for what-ever genes influence cuticular hydrocarbons. The exciting parallelsbetween mate choice in cucumber beetles and vertebrates suggestthat preferences for dissimilar mates may be general across theanimal kingdom.

William A. SearcyExecutive Editor