Some predators chase down their prey. Others organise things so their prey comes to them. Here’s our pick of the predators that set traps - pitfall traps, honeytraps, sticky traps and booby traps, among others - to catch their dinner. And no, they’re not all spiders…
Deadliest traps in the animal kingdom
Margay
The trap set by the margay, a small arboreal cat native to Central and South America, is a psychological one.
In 2005, biologists in Brazil witnessed a group of eight pied tamarins - tiny, critically endangered primates - feeding in a fig tree when a nearby margay emitted sounds mimicking the distress calls of tamarin infants.
The monkeys climbed down to investigate. The alarm was raised before the cat could strike, and the tamarins fled. But the margay’s intentions were clear. It remains the only documented case of a mammal mimicking the vocalisations of its prey as a hunting strategy, although if local folklore is anything to go by, similar mind games are also practised by jaguars, pumas, and ocelots.
Anglerfish
They aren’t called anglerfish for nothing. A characteristic feature of these toothy, wide-mouthed marine predators is the peculiar structure emerging from between their eyes - a fleshy swelling (called an ‘esca’) mounted on the end of a long manoeuvrable spine (the ‘illicium’), which was once part of the dorsal fin. If it looks like a baited fishing rod, it’s because it is one.
Depending on the species, the esca might look like a wriggling worm, shrimp, squid or small fish and, in many deep-sea anglerfish, it is bioluminescent so as to be seen in the darkness. Either way, it lures prey to within snapping distance of the fish’s mouth
A similar fishing technique is employed by the alligator snapping turtle, a huge predatory reptile that lurks in water-bodies in the southeastern USA. Instead of an esca, though, the turtle is equipped with a wormlike extension on its tongue. It just needs to sit motionless with its mouth wide open and then snap it shut on anything that gets too close.
Darwin’s bark spider
Traps are what spiders are famous for. Indeed, the first spider that usually springs to mind is one sitting in an orb web.
No spider builds a bigger orb web than Darwin’s bark spider a Madagascan species that was described only in 2010. The spider specialises in slinging its web over rivers and ponds to catch mayflies and dragonflies.
The supporting threads from which the orb is suspended stretch up to 25m and the silk they are composed of is the toughest of any known biological material - ten times as tough as a comparable thread of Kevlar. The area of the orb itself reaches up to 2.8 sq m. And the whole thing is built by a single spider with a body length of around 20mm.
European mole
Mole tunnels are multi-purpose. Not only do they provide shelter from the elements, but they also make effective traps for earthworms and other burrowing invertebrates. All the mole has to do it patrol its underground labyrinth and collect anything that falls in through the walls and ceiling .
Excess worms that are not eaten immediately are paralysed with a bite to the head and stored alive in tunnel chambers for future consumption. These larders may contain hundreds or even thousands of worms.
Assassin bug
Rigid, piercing, tube-like mouthparts are a defining feature of the ‘true bugs’. Aphids, shield bugs and planthoppers use this proboscis (called a rostrum) to suck sap from plants. Assassin bugs, though, are strict carnivores and wield a vicious, curved rostrum to impale their victims and inject a cocktail of digestive juices. Once the internal organs have been liquefied, the rostrum serves as a straw to suck it all up. Larger species can inflict a painful bite on humans
Like many assassin bugs, Salyavata variegata, a tropical American species that preys on termites, camouflages itself by covering its body in soil and detritus. It then sits by an opening to a termite nest to wait for a victim to come within reach. However, having reduced it to an empty husk, it doesn’t discard the carcass, but uses it instead to set a grisly trap.
Termites are fastidiously house-proud and are compelled to dispose of the remains of their fallen comrades. So the assassin bug dangles the carcass over the entrance to lure more termites from the safety of the nest [https://www.youtube.com/watch?v=Smb2M3UU7VU]. A single bug has been documented catching 31 termites in three hours using the fishing technique.
Trapdoor spider
These ambush predators spend most of their long lives sitting very still waiting for something to happen. But when it does, they spring into action with terrifying efficiency.
The traps they set for their invertebrate prey are the stuff of nightmares. The spiders conceal themselves in a silk-lined burrow capped with a hinged lid that is camouflaged with debris and sits flush with the soil surface.
Trip lines of silken threads radiate from the burrow’s entrance to alert the spider of approaching prey. Should the alarm be sounded, the spider bursts from the burrow, plunges its fangs into the its victim and drags it back into its lair to eat it. The only saving grace is that it’s all over very quickly.
The longevity record for spiders is held by an Australian trapdoor species called Gaius villosus. One female, named ‘Number 16’ as part of a long-term population study in south-western Australia conducted by pioneering arachnologist Barbara York Main [https://www.youtube.com/watch?v=DKI1GaJSNrU], was 43 years old when she died in 2016, having spent her entire life in the same burrow.
Photuris fireflies
Fireflies are famous for the flickering light-shows they put on after dark to attract mates. However, some species wield their bioluminescence more nefariously. In between signalling to potential mates, female Photuris fireflies are signalling to potential meals by mimicking the displays of different firefly species, and then eating any misguided males that turn up on a false promise. Little surprise that Photuris are commonly known as ‘femme fatale fireflies’.
Bolas spider
Another animal that traps prey by exploiting its sexual urges is the bolas spider, named after the weighted ropes used traditionally in South America to catch cattle. This member of the orb-weaver family has reduced its web to a single strand of silk tipped with a heavy, sticky blob, which it twirls around in the air while emitting pheromones that mimic those produced by female moths to attract males.
Arachnocampa
Fireflies are not the only animals that produce light to trap their prey. And spiders are not the only ones to spin webs. In dark wet caves in Australia and New Zealand, there lurk predatory fly maggots that do both at the same time.
Commonly known as ‘glowworms’ (although they are unrelated to the beetles of the same name), the larvae of Arachnocampa fungus gnats [https://www.youtube.com/watch?v=GjW4A-M9L0I] generate a blue-green light from specialised organs in their abdomen that attracts flying insects like moths to a flame. To catch them, the maggots hang long sticky threads of silk from the cave walls and ceiling. Ensnared insects are then hauled up and eaten.
Green heron
Several species of heron – green and nighthave been observed using bait to lure fish within striking range.
The birds will place insects, feathers, berries or even pieces of bread on the water’s surface and wait for fish to investigate. Impressively, they will remove the bait if it starts getting nibbled by fish that are too big to catch. But fish of the right size are snatched from the water with a precision lunge.
This sophisticated behaviour is unlikely to be innate, because only a few individuals of each species seem to fish in this way. It may be that particularly smart individuals are able to hone the technique through trial and error, while others might learn it by watching them.
Meanwhile, in Africa, black herons use their wings as a parasol to create patches of shade that are attractive to their prey
Antlion
Adult antlions are winged insects that look superficially like damselflies (although they are more closely related to lacewings). It’s their larvae that set traps – pitfall traps, to be precise.
To dig one, a larva crawls around in a diminishing spiral in loose dry sand while flicking the grains away with its head as it goes. By the time it reaches the centre, it is in the bottom of a conical pit, the sides of which are as steep as they can be without collapsing.
