Around this time of year, elaborate decorations featuring ghosts, vampires, zombies, witches and werewolves adorn front doors, gardens and shop windows across the country.
But you may be surprised to hear that in the animal world, there are many real-life creatures with similar tendencies to these fictional characters of our Halloween nightmares.
The southern grasshopper mouse (Onychomys torridus) howls at the moon to defend its territory and attract mates, a little like werewolves in films. These nocturnal rodents stand up on their hind legs, point their nose upwards, and produce high-pitched sounds.
Grasshopper mice are voracious carnivores, preying upon scorpions, beetles, grasshoppers, and even other mice. They are also immune to the stings of their favourite food – the bark scorpion (Centruroides sculpturatus). Grasshopper mice can block the chemical pathway that transmits the signal from the venom, essentially numbing themselves to the pain. They then bite off the scorpion’s tail, rendering their prey defenseless to their fate.
These little rodents are so formidable that they will unhesitatingly attack anything that is appropriately sized and considered to be food, even if it might be dangerous.
Small mammals, like grasshopper mice, play crucial ecological roles in their ecosystems. For example, through digging their burrows, they can act as ecosystem engineers (species that modify the environment) creating microhabitats for other species.
The emerald jewel wasp (Ampulex compressa) is a stunningly beautiful and ecologically important species. Not only do they act as casual pollinators for a range of plant species, they are also an essential biocontrol; an organism that controls the population of a pest species.
Over millions of years they have evolved the morbid ability to sting cockroaches and turn them into compliant zombies upon which they lay their eggs. When these eggs hatch, the larvae devour the zombified cockroach from the inside out.
Vampires and witches
Small birds called oxpeckers (Buphagus species) and large ungulates (hoofed mammals) were considered to have a mutually beneficial relationship. When these birds removed pesky ticks and other parasites from their mammalian companions, they were rewarded with a quick, tasty meal. Oxpeckers are often spotted travelling around on the backs of these larger animals.
However, research has highlighted that this relationship may be more complicated than previously thought. Oxpeckers will pick at open wounds to consume blood and flesh – inflicting injuries, preventing wound-healing, and increasing the risk of infection in their hosts.
Witches are well known for creating magical potions but some insects do this too. Bombardier beetles can blast would-be predators with explosive chemicals discharged from their abdomens at temperatures of 100°C. They do this by mixing hydroquinone and hydrogen peroxide within their bodies in a small reaction chamber – their cauldron, if you will – to create this explosion.
Some other insects use chemicals not as a defence mechanism, but to woo a mate. This isn’t an elixir of love, but instead the combination of a chemical and an enzyme (Luciferin and luciferase) that causes a beautiful, if slightly eerie, glow.
The fireflies of the family Lampyridae are actually beetles, whose males flash these colours enthusiastically to attract a waiting female from the undergrowth. Beauty and intrigue aside, fireflies are useful throughout their native range. As larvae they feed on many soft-bodied invertebrates, preventing pest outbreaks and maintaining maintaining a natural equilibrium of species in the soil and leaf litter.
Ghostly frogs
Some frogs in the family Centrolenidae are so translucent, or ghost-like, that they have become known as glass frogs.
Found in the tropical forests of Central and South America, these extraordinary frogs spend much of their lives in the trees and play an important role in the ecosystem. They help regulate insect populations through predation and act as prey for a variety of other species, including in aquatic food webs as tadpoles inhabiting streams. In many ways, they occupy multiple levels of the rainforest ecosystem, linking both terrestrial and freshwater environments.
Come Halloween, many people embellish their houses with plastic skeletons and toilet-paper clad mummies. One insect does a similar thing – the aptly named bone-house wasp (Deuteragenia ossarium). Known for hunting another Halloween favourite, the spider, it decorates the nests it makes for its young with a pile of ant corpses. This morbid tableau provides sensory camouflage for the nest, keeping intruders well away.
All these species are important components of their ecosystems – from keeping pest populations in check or being prey themselves for other animals, to acting as ecological indicators allowing us to monitor environmental changes. Ecological indicator species are key species within ecosystems that help us understand more about how our impact on the planet is affecting other species. Animals respond to different things in the environment, so their populations and behaviours can indicate whether the environment is changing for the better or worse.
These animals may have some rather terrifying tendencies, but unlike the fantasy characters of our horror-film nightmares, they don’t disappear after All Hallows’ Eve. They also have real environmental benefits that endure.
