Signals used in animals
Plenty of animals eat each other, but some of these animals have developed ways to avoid becoming lunch. Bright colours are a common strategy, like in this Granular Poison Frog:
Animals can also give a more active response, such as this video of a Lepidobatrachus frog:
This behaviour is called a ‘pursuit deterrence signal’, which if convincing enough, makes predatory animals re-evaluate the chances of a kill, and possibly give up its pursuit (1, 2).
Tephritid visual signal on jumping spiders
True Fruit Flies (Family: Tephritidae), perform a pursuit-deterrence behaviour (1). When detecting a jumping spider (Family: Salticidae), the fly performs a visual display (called supination), where it faces the threat, brings its wings forward, and walks side-to-side repeatedly (1). The following diagram illustrates this behaviour.
Figure 2. Schedmatic diagram of the jumping spider Paraphidippus aurantius and the visually displaying tephritid fly Anastrepha ludens. The fly moves sideways and brings its wings forward while facing the spider. Reproduced from Rao and Díaz‐Fleischer.
This is the only animal known to perform this strange pursuit-deterrence signal (1). The exact reason for this behaviour has so far been unknown (1), and understanding this behaviour is important as its so novel. Additionally, this behaviour may have conservation implications, as these fruit flies are a well-known agricultural pest in Mexico (1).
Jumping spider response to fly displays
Jumping spiders are visual predators, having the most acute vision of all spiders (3). They are able to move their retina, and hunt their prey much like a cat hunting a mouse (3). Watch an example of this spider’s eyes scanning its surroundings:
When exposed to the fly’s behaviour, however, jumping spiders appear stunned. Not attacking 80% of the time that the fly displays, and simply watching (much like in the previous video) (1). What could cause this? To answer this we need to understand more about jumping spider behaviour.
While scanning, jumping spiders are looking for legs. Do they spot prey, or a potential mate? (3). This judgement is made on the basis of the geometry of the leg pattern of the target animal (1). Jumping spiders use leg displays as parting of their mating dance. Watch the video below to see this:
As it happens, Tephritid flies typically have banding on their wings that resemble a jumping spider’s legs (1). Which might explain why jumping spiders hesitate to attack. In this way, Tephritid flies appear to jumping spiders as a potential mate or even a rival (1). This doesn’t explain everything though as jumping spiders still hesitate to attack flies without this pattern (1).
Why do flies display?
Amongst flies, supination is used to win aggressive encounters with other flies, and to evaluate opponents in contests (2). It might be a way for flies to obtain enough visual information to determine if the jumping spider is a threat (1). Likewise, when exposed to different threats, flies perform the same defensive behaviour, which suggests that this visual defense is not specifically targeted at jumping spiders (2).
Jumping spiders approach prey in preparation of meeting another jumping spider (called sensory bias) (1), and it seems the fly inadvertently exploits this, causing momentarily confusion and generating time to fly away and avoid predation. However, spiders may compensate for this bias by learning. Considered the most intelligent spiders, capable of learning, problem-solving and planning (4), some have overcome this sensory bias. Where spiders repeatedly exposed to supination will attack flies with increasing frequency (5).
No other animal is known to experience a ‘sensory overload’ if you will, as we see in jumping spiders (communication with D. Rao, 2020). Future studies could look at how sensory bias may help other species avoid predation. For example, could a jumping spider’s mating display reduce their likelihod of becoming a bird’s lunch?
Biography
Research on pursuit-deterrence behaviour was performed by Dinesh Rao, a researcher at the Institute of Biotechnology and Applied Ecology Applications (INBIOTECA), Universidad Veracruzana, Mexico.
Initially fascinated by how spiders choose where to make their webs for his Honours project. Dinesh went on to perform a Ph.D at Macquarie university, Sydney, Australia. Where he shed light on how insects respond to silk decorations in spider webs. In addition to pursuit-deterrence signals, Dinesh’s recent work includes conservation biology, where he examines whether spiders can use epiphytes (plants growing on other plants) as a refuge in response to logging and deforestation. Follow Dinesh @dineshraov to find out more!
References
1. Rao, D. and Díaz‐Fleischer, F. (2012), Characterisation of Predator‐Directed Displays in Tephritid Flies. Ethology, 118: 1165-1172. doi:10.1111/eth.12021
2. Aguilar-Argüello, S., Díaz-Fleischer, F. and Rao, D., 2016. Motion-triggered defensive display in a tephritid fly. Journal of ethology, 34(1), pp.31-37.
3. Land, M.F. and Nilsson, D.E., 2012. Animal eyes. Oxford University Press.
4. Harland, D.P. and Jackson, R.R., 2000. Eight-legged cats and how they see: A review of recent research on jumping spiders (araneae: Salticidae). Cimbebasia, 16, pp.231-240.
5. Aguilar-Argüello, S., Díaz-Castelazo, C. and Rao, D., 2018. A predator’s response to a prey’s deterrent signal changes with experience. Behavioural processes, 151, pp.81-88.
Multimedia
Figure 1. “Granulated poison arrow frog”. By Patrick Gijsbers. 21 January 2008. CC BY-SA 4.0. <https://commons.wikimedia.org/wiki/File:Korreldragende-gifkikker-3.jpg>
Figure 2. Rao, D. and Díaz‐Fleischer, F. (2012), Characterisation of Predator‐Directed Displays in Tephritid Flies. Ethology, 118: 1165-1172. doi:<10.1111/eth.12021>
Video 1. “Screaming Budgett’s Frog“. By WizardAngst. 20 Jan 2019. Accessed 10 May 2020. <https://www.youtube.com/watch?v=KfswGei34TI>
Video 2. “Yellow amycine jumping spider, Reserva Canadé, Ecuador“. By wmaddisn 7 Sep 2011. Accessed 9 May 2020. <https://www.youtube.com/watch?v=gvN_ex95IcE>
Video 3. “Peacock Spider Mating Dance“. By Nature on PBS. 16 Nov 2017. Accessed 13 May 2020. <https://www.youtube.com/watch?v=v3HlwwJG85c>
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