These are spectacularly big beetles with fearsome-looking pincers at the head end - but they aren’t interested in us humans – they are focussed on… um… the ladies shall we say, and fighting other males. They live in oak and chestnut woods and are the biggest beetle in Europe. Males fighting for territory (or females!) is normal, high in the trees, and the first beetle to fall down loses everything.
You don’t often see them in Portugal, and in fact I don’t think I have ever seen one, and they are rare. Their struggle to exist as a species is even more complex. The European stag beetle is classified as Near Threatened in the IUCN (International Union for Conservation of Nature) Red List.
Latin name Lucanus cervus, they are big, black and are not only fighting each other, they also fight for survival as they are losing their natural habitat of oak woods. Would you believe they are the subject of a census conducted by thirteen European countries – who have created the European Stag Beetle Monitoring Network to try to increase knowledge about population size, distribution and trends. The network was initiated in 2008 by researchers from eight countries and had expanded to thirteen countries by 2016. Portugal joined the team in 2017, in an effort that brought together researchers and students from the BioLiving association, the Wildlife Unit in the Biology Department of the Aveiro University, the Entomology Portuguese Society and the Nature Conservancy and Forests Institute (ICNF, in Portuguese).
First results of the census in Portugal revealed the existence of a mere 470 to 550 stag beetles, with most of the observations being made in the North and Centre North of Portugal, being Braga, Porto and Aveiro, the districts with the biggest numbers of beetles. The insects were found not only in woods but also in urban zones - in houses, roads and urban parks.
In the summer months they emerge as adult beetles, having spent the previous three or four years as caterpillars inside dead wood, feeding on the roots of oak trees that have died or have dead parts, and they do their bit, unwittingly, to help in regenerating the forests. When they first emerge, they are on a mission to reproduce and will spend their energy reserves in their hunt for a female - and fighting for territory. As they can’t eat solid food, they rely on the fat reserves built up whilst developing as a larvae, but can use their feathery tongue to drink from sap runs and fallen soft fruit.
Now to what they look like. A robust looking creature, its head and thorax (middle section) are generally shiny black, with chestnut brown wing cases. Male beetles appear to have huge antlers, but these are actually over-sized mandibles, used in courtship displays and to wrestle other male beetles. Adult males vary in size from 35mm – 75mm long and tend to be seen flying at dusk in the summer looking for a mate. Female beetles are smaller at between 30 - 50mm long, with smaller mandibles, and they are often seen on the ground looking for somewhere to lay their eggs. They have a lifespan of an amazing 7 years. You wouldn’t think much would predate them, but they are definitely on the menu for different birds, frogs, toads, lizards, foxes, hedgehogs and other insects, especially when the beetle is most vulnerable (and perhaps not paying full attention) in the mating season! If you find one and are tempted to pick one up, beware of those big mandibles that can give a surprisingly strong pinch, so handle them gently by the body only.
Full grown larvae can be up to a massive 110mm long. They’re fairly smooth skinned, have an orange head and legs and brown jaws. They are nearly always found below ground and can be as deep as half a metre down, feeding on decaying wood.
Stag beetles, known as kuwagata mushi in Japanese, are very popular as pets in Japan, much like rhinoceros beetles (kabuto mushi), but I can’t imagine taking one out on a lead for a walk!