Ambush predator

A water bug nymph attacking a fish.

A female goldenrod crab spider (Misumena vatia) capturing the female of a pair of mating flies.

Ambush predators or sit-and-wait predators are carnivorous animals or other organisms, such as some nematophagous fungi and carnivorous plants that capture or trap prey by stealth or by strategy (typically not conscious strategy), rather than by speed or by strength.

Strategy

Animal ambush predators usually remain motionless (sometimes hidden) and wait for prey to come within ambush distance before pouncing. Ambush predators are often camouflaged, and may be solitary animals. This mode of predation may be less risky for the predator because lying-in-wait reduces exposure to its own predators. Furthermore, when a predator cannot move faster than its preferred prey, ambushing its prey is likely to be more efficient than pursuit. Otherwise, active hunting commonly is more effective. There are however many intermediate strategies; for example when a pursuit predator is faster than its prey over a short distance, but not in a long chase, then either stalking or ambushing becomes necessary as part of the strategy.

There are however, many dimensions to predation and many overlapping strategies; for example some predators exploit predictable prey pathways that offer opportunities intermediate between ambush and pursuit. Animals with such strategies include cats of all sizes, crocodiles and some insects such as predators that haunt ant trails. Ambush predators include many fish, snakes, and other reptiles, as well as some mammals, birds, insects and spiders.

In vertebrates

Ray-finned fish

Many ray-finned fish are ambush predators. Depending on the species, their ambushes can occur at the surface of the water, in the main body of the water, or at the bottom.

Alligator gars (Atractosteus spatula) are relatively passive, seemingly sluggish solitary fish, but voracious ambush predators. They are opportunistic night predators and are primarily piscivores, but they will also ambush and eat water fowl and small mammals that may be floating on the surface. Their method of ambush is to float a few feet below the surface, and wait for unsuspecting prey to swim within reach. They lunge forward, and with a sweeping motion grab their prey, impaling it on their double rows of sharp teeth.

The Esociformes are a small order of ray-finned fish, with two families, the Umbridae (mudminnows) and the Esocidae (pikes). Pikes tend to be lie-in-wait, ambush predators, with elongated snouts, long, well-muscled torsos, forked tails, and dorsal and anal fins set well back and opposite each other for rapid acceleration along a straight line, allowing the fish to quickly emerge from cover to capture their prey. Prey capture is facilitated by the impaling of the prey animal on the sharp teeth, after which the pike retreats to cover, turns the prey around, and swallows it, head first. The northern pike, may reach lengths as great as 1.5 m (4.6 ft). Anatomically, the pikes are characterized by the presence of shark-like, maxillary teeth. Mudminnows are much smaller than the related pikes, with usual lengths of less than 20 cm. However, they are also extremely efficient, lie-in-wait, ambush predators, feeding mostly on the invertebrates commonly found in warm backwaters.

Frogfishes catch prey by sudden opening of their jaws.

The Eastern frogfish (Batrachomoeus dubius) is a bottom-dwelling fish endemic to coastal eastern Australia. The fish is found at depths of 1-150 metres along the continental shelf but also estuaries and inshore reefs. It is an ambush predator with a large expandable mouth. It catches prey by suddenly opening their jaws, which enlarges the volume of the mouth cavity up to 12-fold and pulls the prey (crustaceans, molluscs and other whole fishes) into the mouth along with water. The attack can be as fast as 6 milliseconds,

The devil scorpionfish (Inimicus filamentosus) is a piscivorous ambush predator. It is nocturnal and typically lies partially buried on the sea floor or on a coral head during the day, covering itself with sand and other debris to further camouflage itself. It has no known natural predators. When disturbed by a scuba diver or a potential predator, it fans out its brilliantly colored pectoral and caudal fins as a warning. Once dug in, it is very reluctant to leave its hiding place. When it does move, it displays an unusual mechanism of subcarangiform locomotion — it crawls slowly along the seabed, employing the four lower rays (two on each side) of its pectoral fins as legs.

The warteye stargazer (Gillellus uranidea) is a species of sand stargazer which can be found in sandy areas on reefs or among rocks. It is an ambush predator, burying itself nearly completely in the sand and waiting for prey items to come along. It can reach a maximum length of 5 cm.

Northern pike waiting to ambush prey

Mastiglanis asopos is a species of three-barbeled catfish. It is a strictly sand-dwelling species which spends the daytime buried in the top layer of sand. It forages mostly at night and sometimes in the morning. As an ambush predator, it poises in the streamlet channels where water is flowing, supported by a tripod formed by its pelvic and anal fins, spreading both its very long barbels and the filamentous dorsal and pectoral-fin rays, thus forming a kind of "drift-trap". When the fish intercepts food, it will lunge at these food particles; after lunging for a short distance, it will return to its previous hunting spot. This behaviour is similar to that seen in the tripod fish.

Grouper are ambush predators with a powerful sucking system that sucks their prey in from a distance.

The tripodfish Bathypterois grallator uses tactile and mechanosensory cues to identify food; it apparently does not have special visual adaptations to help it find food in the low-light environment. When the fish is perched with its long rays on the ocean floor, it can get food without even seeing it. The tripodfish’s mouth ends up at just the right height to catch shrimp, tiny fish, and small crustaceans swimming by. They seem to prefer to perch on the mud using much elongated fin rays in their tails and two pelvic fins to stand, facing upstream into the current to ambush with the pectoral fins turned forward so the outthrust projecting fins resemble multiple antennae. The fish senses objects in the water with its front fins. These fins act like hands. Once they feel prey and realize it is edible, the fins knock the food into the fish’s mouth. The fish faces into the current, waiting for prey to drift by.

Some fish have the ability to change colour and use this in their ambush behaviour. The Ambon scorpionfish camouflages itself by changing colour and then waits for prey to come close whereupon they lunge forward and inhale the prey.

Cartilagenous fish

Like other members of its family (Squatinidae), the angelshark (Squatina squatina) is a nocturnal ambush predator that buries itself in sediment and waits for passing prey, mostly benthic bony fishes but also skates and invertebrates. It is well-adapted for camouflaging itself on the sea floor, as it has a flattened form with enlarged pectoral and pelvic fins, giving it a superficial resemblance to a ray.

The tasselled wobbegong (Eucrossorhinus dasypogon) feeds on fish, crustaceans, and cephalopods. Its capacious mouth allows large prey to be swallowed, with one documented case of a 1.3 m (4.3 ft) long individual consuming a 1.0 m (3.3 ft) long brownbanded bamboo shark (Chiloscyllium punctatum). During daytime, this species is an opportunistic ambush predator. It preys upon schooling nocturnal fishes such as squirrelfishes, soldierfishes, and sweepers that often shelter in the same cave. Tiny fishes and crustaceans have been seen settling atop the resting wobbegong's head, attracting larger fishes that are in turn attacked by the wobbegong. Observations in captivity have further revealed that this species engages in active luring behaviour. When it perceives food nearby, it begins to slowly wave its tail back and forth; its caudal fin resembles a small fish, complete with a dark eyespot at the base. The shark typically rests with its head elevated, which places it within striking distance of any prey drawn by its tail.

Reptiles

Crocodilians

Crocodile ambushing wildebeest crossing the Mara River

The Nile crocodile (Crocodylus niloticus) possesses unusual predatory behaviour as it has the ability to hunt both within its natural habitat and out of it, which often results in unpredicted attacks on almost any other animal up to twice its size. Nile crocodiles are apex predators throughout their range. In the water, they are an agile and rapid hunter, using both movement and pressure sensors to catch any prey unfortunate enough to place themselves inside or near the waterfront. Most terrestrial prey are caught by ambush attacks when the animal approaches water to drink. The crocodile slowly comes closer, most of its body underwater, sometimes only its eyes and nostrils visible. On other occasions more of its head and upper body visible. The attack is sudden and unpredictable. The crocodile lunges its body out of the water and grasps its prey. The teeth of a crocodile are not for tearing up flesh but to bite deep in to the prey and hold on to it. The immense bite force, which may be as high as 22,000 N in large adults, ensures the prey item can't escape from the grip. The prey is usually killed by drowning or being torn apart by "death rolls". On land, the Nile crocodile can gallop to chase prey. Most hunting on land is done at night by lying in ambush near forest trails or roadsides, up to 50 m from the water's edge.

Lizards

The mulga dragon (Caimanops amphiboluroides) is a species of agamid lizard found in Western Australia. The species grows up to 25 cm long. The patterning over the legs and body is grey and brownish streaks. This provides an excellent camouflage on mulga trees, its usual habitat, The mulga dragon generally remains motionless and unobserved, allowing it to be an ambush predator and to elude animals that would prey on it.

Turtles

Cantor's giant softshell turtle ambushes prey from the mud of river bottoms.

Komodo dragons (Varanus komodoensis) are carnivores. Although they eat mostly carrion, they will also ambush live prey with a stealthy approach. When suitable prey arrives near a dragon's ambush site, it will suddenly charge at the animal and attempt to grasp the underside or the throat. The Komodo dragon's diet is wide-ranging, and includes invertebrates, other reptiles (including smaller Komodo dragons), birds, bird eggs, small mammals, monkeys, wild boar, goats, deer, horses, and water buffalo. The Komodo dragon hunts in the afternoon, but stays in the shade during the hottest part of the day. These special resting places, usually located on ridges with cool sea breezes, are marked with droppings and are cleared of vegetation. They serve as strategic locations from which to ambush deer. Komodo dragons have been observed knocking down large pigs and deer with their strong tails.

Cantor's giant softshell turtle (Pelochelys cantorii) can grow up to approx 2 m in length. It is an ambush predator and primarily carnivorous, feeding on crustaceans, molluscs and fish (although some aquatic plants may also be eaten). The turtle spends 95% of its life buried and motionless, with only its eyes and mouth protruding from the sand. It surfaces only twice a day to take a breath. Similarly, the New Guinea giant softshell turtle (Pelochelys bibroni) is considered to be an ambush predator.

Snakes

Malabar pit viper in typical ambush pose of snakes.

The Eastern green mamba is a diurnal, arboreal, secretive species of snake. It tends to spend most of its time above the ground in relatively dense brush, where it is well camouflaged. This species is not commonly found on land unless motivated by thirst, prey, or the need to bask in the sun (thermoregulation). It is an alert, nervous, excellent climber and extremely agile snake. In a study of the movement patterns of two adult specimens of this species over a 27-day period, the researcher found their activity range areas to be very small compared to other predators who actively hunt prey rather than ambush them. This is in contrast to most elapid species, including other mambas, who tend to actively hunt or forage for prey. The study's preliminary evidence sheds some light on this species' method of hunting prey and suggests that it may be an ambush predator due to the sit-and-wait behaviour displayed. However, this evidence does not preclude active foraging by this species; one specimen systematically hunted a sleeping bat.

The Antiguan racer (Alsophis antiguae) is a diurnal snake which is an ambush predator, primarily eating lizards. While the species sometimes hunts for its food, it is more typically an ambush predator, waiting for prey with most of its body buried beneath leaves. The racer typically eats a lizard once every two weeks.

In invertebrates

Insects

An example of an ambush predator and its trap

Closeup of an antlion larva

Sand pit trap of an antlion

Some ambush predators build traps to capture their prey. Lacewings are a flying insect in the order Neuroptera. In some species, their larval form, known as the antlion, is an ambush predator. Eggs are laid in the earth, often in caves or under a rocky ledge. The juvenile creates a small, crater shaped trap. The antlion hides under a light cover of sand or earth. When an ant, beetle or other prey slides into the trap, the antlion grabs the prey with its powerful jaws.

The majority of the 2,400 species of praying mantises are ambush predators, although some ground and bark species actively pursue prey. Species that are predominantly ambush predators camouflage themselves and spend long periods standing perfectly still. They largely wait for their prey to stray within reach, but most mantises chase prey if it strays closely enough. In pure ambush mode, a mantis lashes out at remarkable speed when a target does get within reach. When the prey is a butterfly or other flying insect, the mantis snatches it out of the air. Praying mantises are deliberate when they move, and only do so when there is good reason to. When they do move, they often travel forward while gently rocking back and forth. This helps them to blend in with the bush or tree on which they are climbing, as it sways in the breeze.

The Reduviidae, also known as "assassin bugs", are a large family of the Hemiptera order. They are slightly unusual among the Hemiptera because almost all are terrestrial ambush predators (most other predatory Hemiptera are aquatic). Though there are spectacular exceptions, most members of the family are fairly easily recognizable: they have a relatively narrow neck, sturdy build and formidable curved proboscis (sometimes called a rostrum).

Arachnids

The atypical tarantulas, or purseweb spiders, (family Atypidae) build a silken tube parallel to the surface of the ground. While up to 8 cm of the tube lie on the ground, about 20 cm are buried vertically. The spider rests at the bottom of the tube. When prey walks on the exposed part, the spider, alerted by the vibrations, stabs it through the silk, cuts the web and drags it inside to be eaten.

The European yellow-tailed scorpion (Euscorpius flavicaudis) is a small, black scorpion measuring about 35–45 mm long. It is a fossorial scorpion with relatively large, strong claws (pedipalps) and a short, thin tail. It is an ambush predator, lying motionless at the entrance to its lair, but moving quickly to capture prey that wander past. The main prey of E. flavicaudis are woodlice, although most small insects are taken. Scorpions may go for long periods of time without food.

Malacostraca

Polycheles typhlops is a species of blind, deep-water, decapod crustacean. It probably acts as an ambush predator, hiding buried in the sediment with its claws raised above the surface. Its main prey are bony fish and other crustaceans, such as shrimp, mysids and amphipods.

Cephalopods

The World's largest invertebrate, the colossal squid (Mesonychoteuthis hamiltoni), roams the deep waters of the Southern Ocean where it is believed to be an ambush predator of prey such as chaetognatha, large fish such as the Patagonian toothfish, and other squid. It is thought to have a slow metabolic rate, needing only around 30 grams (1.1 oz) of prey daily. A single 5 kg Antarctic toothfish provides enough nourishment for a 500 kg colossal squid to survive for 200 days. These estimates of its energetic demands suggest it is a slow-moving ambush predator which uses its large eyes primarily for predator detection rather than active hunting.

Asteroidia

Leptasterias tenera is a small starfish with five arms and a slow growth rate. It can grow to a diameter of 16 cm. Leptasterias tenera is an ambush predator. It remains stationary on the seabed for long periods, snaring any small crustaceans which come into contact with it, gripping them with its tube feet and pedicellariae and flexing its arms to transfer the prey to its mouth. Large items are pushed as far as they will go into the pyloric stomach but only the portion inside is digested at first.

In microorganisms

Pfiesteria is a genus of heterotrophic dinoflagellates that has been associated with harmful algal blooms and fish kills. Research suggests that Pfiesteria behaves as an ambush predator and utilizes a "hit and run" feeding strategy by releasing a toxin that paralyses the respiratory systems of susceptible fish, such as menhaden, thus causing death by suffocation. It then consumes the tissue sloughed off its dead prey.

In extinct animals

The thylacine was exclusively carnivorous. Its stomach was muscular, and could distend to allow the animal to eat large amounts of food at one time, probably an adaptation to compensate for long periods when hunting was unsuccessful and food scarce. Analysis of the skeletal frame and observations of it in captivity suggest that it preferred to single out a target animal and pursue that animal until it was exhausted. Some studies conclude that the animal may have hunted in small family groups, with the main group herding prey in the general direction of an individual waiting in ambush. Trappers reported it as an ambush predator. Although the living grey wolf is widely seen as the thylacine's counterpart, it has been proposed that the thylacine was more of an ambush predator as opposed to a pursuit predator. In fact, the predatory behaviour of the thylacine was probably closer to ambushing felids than to large pursuit canids. Consequently, at least in terms of the postcranial anatomy, the vernacular name of "Tasmanian tiger" may be more apt than "marsupial wolf".

External links

• Predation lecture University of Washington