Mimic Spotlight: The Superb Lyre Bird (Menura superba)

Throughout the semester I've predominantly discussed visual mimicry, so I thought for the last "official" post I'd cover something a bit different; the Superb Lyre Bird. 

The Superb Lyre Bird (Menura superba) is a fairly well known example of vocal mimicry among birds, having the most complex syrinx of any Passerine (song bird) which gives it an unrivaled vocal repertoire and ability to mimic almost any sound imaginable. 

Figure 1: Superb Lyre Bird (Menura superba)

The song of the Lyre Bird is comprised of a mixture of its own song and a number of mimicked sounds/noises; Lyrebirds most commonly mimic other birds, or other animals (eg; koalas and dingoes). The male Lyrebirds call throughout the year, but are most intense during the breeding season (June to August) when they call and dance (showing off their tail feathers) to attract a female. The female Lyrebirds can also sing, but they are generally less skilled than the males (That's sexual selection for you).

Figure 2: Superb Lyre Bird (Menura superba)

FUN FACTS TIME! 

In addition to learning sounds from their environment, Lyrebirds can pass on sounds to other individuals, enabling songs to be passed on from generation to generation. Flute-like calls have been observed in a small number of Lyrebird individuals, and thanks to research by Neville Fenton after he observed such flute mimicry in 1969, it was discovered that this flute mimicry was originally learned by a pet Lyrebird in the 1930s.

Individual Lyrebirds have been known to mimic some very strange and unique sounds. Some of the more abstract examples of Lyrebird mimicry include; computer game sounds, car alarms, chainsaws and even the human voice.

- National Film and Sound Archive, Sounds of Australia
- Tapper, James (7 May 2006). "The nation's favourite Attenborough moment". Daily Mail (Daily Mail Online).
- Lill, Alan (2004), "Family Menuridae (Lyrebirds)", in del Hoyo, Josep; Elliott, Andrew; Christie, David, Handbook of the Birds of the World. Volume 9, Cotingas to Pipits and Wagtails, Barcelona: Lynx Edicions, pp. 484–495
- Reilly, P.N. (1988). The Lyrebird: A Natural History. Kensington, NSW: New South Wales University Press

- Figure 1: http://ih2.redbubble.net/image.8010946.1140/flat,550x550,075,f.jpg, photo by Donovan Wilson, retrieved 29/05/14.
- Figure 2: http://www.duadepaton.com/wp-content/uploads/2013/06/350-Superb-Lyrebird-North-Nowra-1061.jpg, unknown photographer, retrieved 29/05/14

Mimic Spotlight: The AntySpider (hurr hurr, puns)

Much like the Orchid Mantis I talked about in March, Myrmarachne melanotarsa uses mimicry both defensively and aggressively. This jumping spider (See Figure 1) is one of many jumping spider species which mimic ants, specifically the cocktail ant (Crematogaster sp.) in M. melanotarsa's case. 

Figure 1: Myrmarachne melanotarsa

Many jumping spiders (Salticidae) are afraid of ants, as they are often preyed on by the 6-legged fiends. Additionally ants are well-protected against salticids which might view ants as potential prey. For this reason it is common in ant-adverse jumping spiders, such as Menemerus sp. for the females to abandon their broods when in the presence of ants more often than when in the the presence of other salticids. Ants have trouble navigating the web-built nests of jumping spiders, and hence it is usually safe for mothers to leave their brood unattended for a short time as the risk of predation by ants is low.

Our ant-mimic uses this behaviour to its advantage, as it raids the abandoned nests of the aforementioned Menemerus sp. for eggs and newly-born young. Unlike the ants it mimics, M. melanotarsa has no difficulty entering the nest (it is a spider, after all). The figure below shows that M. melanotarsa is often mistaken for an ant by the females of  Menemerus sp - indicating a successful mimetic display by M. melanotarsa. 

Figure 2: Frequency of test spider (Menemerus sp.) females remaining inside nest with hatchlings or vacating nest when surrounded by groups of 20 individual ants (Crematogaster sp.), ant-like salticids (M. melanotarsa), non-ant-like salticids (Menemerus sp. and Pseudicius sp.), midges (Chaoborus sp.) and empty stimulus chambers (control). Black = outside nest; grey = inside nest.

In addition to the aggressive uses of its mimicry, M. melanotarsa also gains some protection from its ant disguise. As mentioned earlier, ants pose a serious threat to salticids - so jumping spiders tend to avoid ant encounters whenever possible. As a result, salticids which prey on other jumping spiders often mistake M. melanotarsa as an ant, and hence, our mimic avoids being eaten. Success. 

While Batesian mimicry relies on being seen by a potential predator, aggressive mimicry relies on blending in; not being seen. Other salticids, such as Cosmophasis bitaeniata, use this ant disguise to infiltrate ant nests and prey on the eggs. It is due to this that ant-mimicing spiders are generally regarded as being aggressive mimics, because the defensive aspect of their mimicry is a considered a secondary benefit.

- Nelson, X. J. and Jackson, R. R. 2009, ' Aggressive use of Batesian mimicry by an ant-like jumping spider', Biology Letters, vol. 5, pp. 755-757

- Figure 1: http://img3.rnkr-static.com/user_node_img/50007/1000134056/full/myrmarachne-melanotarsa-photo-u3.jpg, unknown photographer, retrieved 02/05/14
- Figure 2: Nelson, X. J. and Jackson, R. R. 2009, ' Aggressive use of Batesian mimicry by an ant-like jumping spider', Biology Letters, vol. 5, pp. 756

Now You See Me, Now You Don't

Usually, mimicry is a permanent state (more so in vertebrates than invertebrates). But this is not the case for the bluestriped fangblenny (Plagiotremus rhinorhynchos) which can 'turn off' its mimetic appearance at will.

The fangblenny mimics the juvenile bluestreak cleaner wrasse (Labroides dimidiatus), which is characterised by an electric blue stripe on each side its black body. In its non-mimetic colouration, the fangblenny is orange or olive/brown and shoal with other reef fish - predominantly red-cheeked anthias (Pseudanthias huchti), purple anthias (Pseudanthias tuka) and shoulderspot wrasses (Leptojulis cyanopleura) (Cote and Cheney, 2005).

Figure 1: a) mimetic bluestriped fangblenny b) juvenile bluestreak cleaner wrasse (model)

c) and d) orange and olive/brown forms of non-mimetic bluestriped fangblenny

In its mimetic form, the fangblenny can blend in with the harmless cleaner wrasse and ambush unsuspecting prey (an example of aggressive mimicry). In its non-mimetic form, the fangblenny also ambushes prey; however no disguise/deception is utilized in this instance.

- Cote, I. M. and Cheney, K. L. 2005, 'Choosing when to be a cleaner-fish', Nature, vol. 433, pp. 211.

- Figure 1: (Cote and Cheney, 2005), retrieved 09/04/14.

Introduction to Aggressive Mimicry

Aggressive mimicry is a form of mimicry in which predators deceive potential prey by making signals to (indirectly) influence prey behaviour (Jackson and Cross, 2013). Basically, aggressive mimicry is the opposite of Batesian Mimicry in the sense that the prey is being fooled, rather than the predator.

Much like other types of mimicry, aggressive mimicry can be expressed in many different ways. Predators might mimic the physical appearance of a harmless species to allow them to approach unsuspecting prey. An example of this is the Zone-Tailed Hawk (Buteo albonotatus) shown in Figure 1, which resembles the common Turkey Vulture (Cathartes aura) in plumage colour, shape and soaring behaviour. Zone-Tailed Hawks soar with groups of Turkey Vultures, but breaks formation to dive and catch prey. It is believed that the prey of the Hawk do not feel threatened by the Turkey Vultures and therefore by blending in with said Turkeys, the hawk has a better chance of catching prey (Willis, 1963).

Figure 1: A Zone-Tailed Hawk (Buteo albonotatus)

Alternatively, predators might lure prey by pretending to offer food, a mate, or something else that the prey species would want/need. This second type is much more interesting in my opinion, as the mimetic predators in question have adapted some amazing features and behaviours. One such example is the Assassin Bug (Stenolemus bituberus), which hunts spiders by pretending to be a meal stuck in the spider's web. It does this by plucking the silk of a spider's web in a way which sends a signal to the spider that there is prey in the web. Once the spider approaches to investigate, the Assassin Bug strikes (as shown in Figure 2)! What's even more amazing is that the Assassin Bug knows the difference between the characteristic vibrations of a prey and the characteristic vibrations of a falling leaf or another spider. Without this skill, the Assassin Bug wouldn't be able to catch spiders in the way that it does (Wignall and Taylor, 2011).

Figure 2: an illustration of an Assassin Bug (Stenolemus bituberus) tricking an unlucky spider

- Jackson, R. R. and Cross, F. R. 2013, 'A cognitive perspective on aggressive mimicry', Journal of Zoology, vol. 290, pp. 161-171.
- Wignall, A. E. and Taylor, P. W. 2011, 'Assassin bug uses aggressive mimicry to lure spider prey', Proceedings of the Royal Society, vol. 278, pp. 1427-1433.
- Willis, E. O. 1963, 'Is the Zone-Tailed Hawk a Mimic of the Turkey Vulture?', The Condor, vol. 65, no. 4, pp. 313-317.

- Figure 1: http://upload.wikimedia.org/wikipedia/commons/8/8d/ZonetailedHawk2.jpg, Photographer: Stolz, G. M., retrieved 01/04/14
- Figure 2: http://images.smh.com.au/2010/10/27/2011409/Wilcox_bug-420x0.jpg Author: Cathy Wilcox, retrieved 01/04/14

Introduction to Müllerian Mimicry

Along with Batesian mimicry, Müllerian mimicry is the other major form of defensive mimicry. In contrast to Batesian mimicry, Müllerian mimicry does not involve any deception, as all species involved are unpalatable. Müllerian mimicry is defined as two or more unpalatable prey species sharing a similar appearance (eg: colours, patterns, etc) (Huheey, 1976).

In practise however, the difference between Batesian and Müllerian mimicry isn't black and white; there's actually a sliding scale of (un)palatability among mimetic species (ie: a mimetic species might be entirely harmless, just as dangerous as their model, or somewhere in-between) (Huheey, 1976).

An example of Müllerian mimicry is found in the Viceroy (Limenitis archippus) and Monarch (Danaus plexippus) butterflies shown in Figure 1, where both species are unpalatable. Until recently, the Viceroy was believed to be palatable - which would have made this relationship an example of Batesian mimicry (Ritland and Brower, 1991).

Figure 1: Similarities between Viceroy (top) and Monarch (bottom) butterflies.

While Batesian mimicry could be considered a form of antagonistic symbiosis (one species benefits at the expense of others), Müllerian mimicry is a mutualistic relationship between species. This is because mimic and model alike benefit from the shared 'advertisement' as it makes it easier for predators to recognize (and avoid) certain colourations/patterns in unpalatable prey species (Huheey, 1976); which, as it happens, also benefits the predator species .... Good guy Müllerian mimicry? 

- Huheey, J. E. 1976, 'Studies in Warning Coloration and Mimicry. VII. Evolutionary Consequences of a Batesian-Müllerian Spectrum: A Model for Müllerian Mimicry', Evolution, vol. 30, no. 1, pp. 86-93.

- Ritland, D. B. and Brower, L. P. 1991, 'The viceroy butterfly is not a batesian mimic', Nature, vol. 350, pp. 497-498.

- Figure 1: http://upload.wikimedia.org/wikipedia/commons/6/63/BatesMimButter.JPG, Photographer(s): D. Gordon, E. Robertson and Derek Ramsey, retrieved: 29/03/14

Mimic Spotlight: Orchid Mantis (Hymenopus coronatus)

I find the Malaysian Orchid Mantis (Hymenopus coronatus) fascinating. Not only is it a beautiful and just generally cool looking insect, but it also expresses both mimicry and mimesis throughout its life-cycle. 

I mentioned in my first post that mimicry and camouflage are different from one another. Camouflage is used by animals to make themselves less visible - via body colouration, patterns, or morphological structures (Stevens and Merilaita, 2008) to blend into the background. This is distinct from mimicry, where animals are still perfectly visible. Mimesis is an area of overlap between the two, where an organism resembles a specific object, such as a leaf or bird dropping (Pasteur, 1982).

Figure 1: A juvenile Orchid Mantis

Hymenopus coronatus, shown in Figure 1, expresses (aggressive) mimesis in its juvenile and adult forms, where it mimics parts of the flower of a orchid. The colours and shapes of the orchid mantis act as visual cues to pollinators (prey of the orchid mantis), attracting them (O'hanlon et al., 2013). The mantis' four walking legs look like petals, whilst the two front limbs are used to grasp any prey unfortunate enough to get too close. 

Figure 2: An adult Orchid Mantis

Adult orchid mantises (as shown in Figure 2) do not resemble orchid flowers to the same extent that juveniles do. However, they still retain femoral lobes and a similar white colouration, both of which could still be attractive to pollinators (O'hanlon et al., 2013). It is also entirely possible that the orchid mantis' resemblance to an orchid flower in the juvenile stage helps it hide from predators; therefore, as individuals mature and are better able to defend themselves, there may be less need to be such a convincing mimic.

Figure 3: Orchid Mantis nymph

Whilst the older Orchid Mantises mimics orchid flowers (mimesis), the first stage nymphs (shown in Figure 3) mimic members of the Reduviidae family (mimicry). This is a form of Batesian mimicry, as the model insect tastes pretty awful and also has a powerful bite (Gurney, 1951) and therefore, by resembling the model, the nymph can deter potential predators. 

- Gurney, A. 1951 'Praying mantids of the U.S, native and introduced', Annual Report of the Board of Regents of the Smithsonian Institution, vol. 105, no. 1, pp. 344-345.
- O'hanlon, J., Li, D. and Norma-Rashid, Y. 2013, 'Coloration and Morphology of the Orchid Mantis Hymenopus coronatus', Journal of Orthoptera Research, vol. 22, no. 1, pp. 35-44.
- Pasteur, G. 1982, 'A Classificatory Review of Mimicry Systems', Annual Review of Ecology and Systematics, vol. 13, no. 1, pp. 169-199.
- Stevens, M. and Merilaita, S. 2008, 'Animal camouflage: current issues and new perspectives', Philosophical Transactions of The Royal Society, vol. 364, no. 1, pp. 423-437.

- Figure 1: http://www.themagazine.ca/cms/wp-content/uploads/2011/03/Malaysian-orchid-mantis.jpg By Unknown photographer, retrieved: 22/03/14
- Figure 2: http://upload.wikimedia.org/wikipedia/commons/3/36/Insect_camouflage_PP08338.png Photographer: Philipp Psurek, retrieved: 22/03/14
- Figure 3: http://www.nature-china.net/home/attachment/201102/28/195028_1298915776QH1R.jpg Unknown photographer, retrieved 22/03/14

Introduction to Batesian Mimicry

Prey species use a huge variety of defense mechanisms to avoid being eaten; some species spray formic acid, some species confuse their attacker by suddenly jumping into the air, and some species simply run away as fast as they can. Other species leave a bad taste, or sometimes make their attacker ill, when eaten. Whilst this usually doesn't help the individual being eaten (rest in many pieces, little guy), predators learn to avoid that particular species - resulting in protection for a whole population of that prey species. 

Often, prey will announce how dangerous or bad-tasting they are by having distinct markings, or colours. Enter center stage, the Batesian Mimic (who, spoiler alert, lies). Batesian mimicry is a type of defensive mimicry which involves a non-harmful species looking like a harmful species (called a 'model') to avoid being eaten (Allen and Cooper, 1995).

Figure 1: Mimetic Scarlet King Snake and its model, the Eastern Coral Snake

Logic dictates that Batesian mimicry would be frequency-dependant (ie: the number of mimetic individuals would be limited by the number of model individuals), and this has been shown to be the case is the majority of mimetic species such as the Scarlet King Snake shown in Figure 1, where the frequency of predation on the mimic species decreased with increased relative abundance of the model species (Pfennig et al., 2001). 

This is not always the case, however, as hoverflies are more abundant than their wasp model species (Dittrich et al., 1993). In cases such as this, the model species is usually so dangerous that it is thought that predators will avoid any prey which looks like the model, even if the chance of catching a harmless mimic is much higher than catching the actual dangerous species; "better safe than sorry" springs to mind.

Interestingly, it has been suggested that mimicking a species that can easily escape a predator can be just as an effective method to avoid predation as mimicking a harmful species. It is suspected that a certain predator could associate markings/colours of a very agile prey species as being a "waste of energy" and will not try to catch said species. As such, a less agile species (that would otherwise be easy to catch and eat) could mimic the "waste of energy" model and hence, predators would not bother trying to eat it (Gibson, 1974).

- Allen, J. A. and Cooper, J. M. 1995, ‘Mimicry’, Journal of Biological Education, vol. 29, no. 1, pp. 23-26
- Dittrich, W., Gilbert, F., Green, P., McGregor, P. and Grewcock, D. 1993, 'Imperfect mimicry: a pigeon's perspective', Proceedings of the Royal Society of London, vol. 251, no. 1332, pp. 195-200.
- Gibson, D. O. 1974, 'Batesian mimicry without distastefulness?', Nature, vol. 250, no. 1, pp. 77-79.
- Pfennig, D. W., Harcombe, W. R. and Pfennig, K. S. 2001, 'Frequency-dependent Batesian mimicry', Nature, vol. 410, no. 1, pp. 323.

- Figure 1: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitNsKjhlsSlWcgdJytSdJiVK6ez4yB3Z_-aMSUENLRV6ONjT-eIP-dGLRN6qe3bKocz3bxaYlrgl4hQSWz7I_pO0cDIDlkYUoBUN6M5VHiLNuTK4570r5BIWzKZR9Cv_ud-qmpkvwv5xGq/s1600/Coral_snake_mimics.gif