Classification, Origin, and Evolution
Amphibians are the oldest living class of animals in the world and they were the first to colonise the land, their name Amphibian is derived from the Greek words amphi and bios meaning ‘both’ and ‘life’ respectively – their anatomy is completely different to reptiles as they have no scales and need to be near water to breed, see table 5 for classification (Coborn, 1992, McCarthy, 1993 and Manning, 2008). Strawberry poison dart frogs have many common names including: red-and-blue, flaming, dart and arrow, they are commonly known as dendrobates pumilio in older literature – they are found in South America, see figure 8 (IUCN, 2015b). See figure 6 for the most common colouration and figure 7 for the full lineage of the strawberry poison dart frog.
Fig 6. The most common colour for a strawberry poison dart frog (The Nature Conservancy, 2016).
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Table 5 – Strawberry Poison Dart Frog classification (UniProt, 2016b).
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Fig 7. Full taxonomic lineage of the strawberry poison dart frog (UniProt, 2016b).
These frogs have delicate, moist porous skin that is protected by a layer of mucous, this is sloughed periodically and eaten to gain extra nutrients – this type of skin allows poison dart frogs to defend themselves from predators, parasites, and infection (fungal and bacterial) by being toxic to touch (Clarke, 1993, Bruins, 2006, Manning, 2008 and Holmes et al., 2009). It is an alkaline toxin that is derived from eating termites, ants, beetles, mites, and other leaf-litter arthropods which is why captive bred poison dart frogs are not toxic (Bruins, 2006 and Jackson, 2011). Adult poison dart frogs are insectivorous and will swallow their prey whole, they hold their prey by using tiny peg-like teeth – unlike other amphibians, the caecilians, frogs have shortened fused vertebrae and developed extremely muscular legs (Attenborough, 1979, Coborn, 1992 and Manning, 2008). These strong legs not only help them to move around on the ground but helps them to escape predators (Attenborough, 1979). Strawberry poison dart frogs have many evolutionary adaptations and traits to cope with their environment, these are mostly advantageous but can also be disadvantageous, see table 6.
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Fig 8. Natural distribution of strawberry poison dart frog (IUCN, 2015a).
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Table 6 – Evolutionary traits of the strawberry poison dart frog (Coborn, 1992).
Natural Behaviour
Male poison dart frogs will use their bright colours to defend territories, protect their young and themselves from predators – they also attract females with a far-reaching call (see video 6) and will wrestle other males (see video 4); it has been discovered that females will choose a brighter male when picking a suitable mate (Clarke, 1993, Nguyen and Whittaker, 2016 and WAZA, 2016). Females will lay their eggs on leaves were a male will guard the small clutch and keep them moist until they hatch – this is advantageous to the offspring by increasing their chances of survival; however, the male is left exposed to predators and he cannot go find food whilst standing guard(WAZA, 2016).
Poison dart frogs prefer to live in the leaf-litter of tropical rainforests rather than climb trees like other frogs as they are diurnal and terrestrial, although the female will transport her newly hatched young one by one up a tree to find a bromeliad filled with water (see video 5) – the female will lay an infertile egg for the tadpole to feed on (Birkhead et al., 1994 Zimmermann, 1995, Jackson, 2011 and WAZA, 2016). These frogs have adapted to a two-stage life cycle by starting life in the water gathered in bromeliads and then moving to land once metamorphosis has been completed – they are also ectotherms and rely on the environment to regulate their body temperature at both stages (Manning, 2008, Nguyen and Whittaker, 2016 and WAZA, 2016). This two-stage life cycle accompanied with the parental care a strawberry poison dart frog provides means they have a higher survival rate and abundance when compared to other poison dart frogs. However, this can be disadvantageous as the tadpoles are dependent on their parents and cannot escape the bromeliad making them easy pickings for a predator and they could starve if their parents die.
Poison dart frogs prefer to live in the leaf-litter of tropical rainforests rather than climb trees like other frogs as they are diurnal and terrestrial, although the female will transport her newly hatched young one by one up a tree to find a bromeliad filled with water (see video 5) – the female will lay an infertile egg for the tadpole to feed on (Birkhead et al., 1994 Zimmermann, 1995, Jackson, 2011 and WAZA, 2016). These frogs have adapted to a two-stage life cycle by starting life in the water gathered in bromeliads and then moving to land once metamorphosis has been completed – they are also ectotherms and rely on the environment to regulate their body temperature at both stages (Manning, 2008, Nguyen and Whittaker, 2016 and WAZA, 2016). This two-stage life cycle accompanied with the parental care a strawberry poison dart frog provides means they have a higher survival rate and abundance when compared to other poison dart frogs. However, this can be disadvantageous as the tadpoles are dependent on their parents and cannot escape the bromeliad making them easy pickings for a predator and they could starve if their parents die.
Vid 4. Two male strawberry poison dart frogs wrestling (Globalzoo, 2010).
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Vid 5. A female strawberry poison dart frog transporting her offspring (Whitefeel Blak, 2012).
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Vid 6. A male strawberry poison dart frog calling (Bolton, 2008).