Buzz
Nuytsia@Tas, Flickr // CC BY-NC-SA 2.0
Provoke a cat, and it may arch its back, puff up its fur, bare its teeth, and hiss at you. This dramatic reaction is called a deimatic or startle display, a tactic used to intimidate or distract a threat, giving the animal a chance to flee. Many creatures employ similar strategies. Some displays genuinely signal the animal’s defenses, such as toxins, while others are mere bluffs. Regardless, the display is only effective if it deters a predator before an attack occurs. There’s little point in warning a predator about your defenses or trying to scare it off once it’s already attacking you. Logically, a startle display should be clear and occur before an attack.
This is typically the case, but Australia’s mountain katydid (Acripeza reticulata) is an exception.
These cricket relatives, about the size of a thumb, are slow-moving and awkward. They protect themselves by releasing bitter, toxic chemicals from their abdomens, which are harmful to birds and mammals but strangely act as aphrodisiacs for certain insects. To deter predators, they perform a startling display involving vomiting and revealing the bright red, blue, and black stripes hidden under their otherwise plain brown wings. While striking, zoologist Kate Umbers noted that this display appears ineffective because it occurs after the katydids have already been attacked.
In her fieldwork, Umbers discovered that she could easily handle the bugs without issue. Only after she picked them up did they attempt to deter her or reveal their defensive mechanisms. While this posed no threat to the bugs in her care, such a delayed reaction would be ineffective if they were caught by a predator instead of a researcher.
Perplexed by this behavior, Umbers collaborated with Johanna Mappes, known for her fascinating studies on snakes, to analyze the defensive responses of 40 additional katydids in a controlled setting. Most of the insects remained unresponsive when exposed to stimuli like air puffs, simulated bird movements, or nearby tapping. They only displayed their vivid colors and regurgitated when physically touched or grabbed.
Although a post-attack startle display seems illogical, Umbers and Mappes explain that it aligns with the katydid’s unique traits. Unlike many animals that startle predators and then flee, katydids lack the agility to escape quickly. They are slow, awkward, and limited in their jumping ability, with only males capable of flight. Their strengths lie in their chemical defenses and durable, camouflaged wings that protect their abdomens and help them blend into their surroundings.
The researchers propose that the katydid’s display isn’t delayed but rather part of a layered defense strategy that defies conventional norms. They believe the insect prioritizes camouflage to evade detection. If discovered and attacked, its resilient wings shield it during the initial assault, while its toxins and startling display prevent further attacks. By reserving the display until necessary, the katydid avoids prematurely revealing itself to potential predators.
Umbers and Mappes aim to test their theory by observing how the katydid’s defenses perform against natural predators. However, they face a challenge: the predators of these katydids remain unidentified. Umbers noted the presence of ravens and magpies in the bugs’ habitat, making them likely candidates. These birds often probe their prey with their beaks before consuming them, giving the katydid an opportunity to deploy its defenses after initial contact but before becoming a meal.
