Malevolent Designer - It's A Frog Eat Frog World Out There!

Green and golden frog, Litoria aurea, female eating a juvenile striped marsh frog, Limnodynastes peronii

Gould, J., & Beranek, C. T. (2024). (CC BY 4.0)

Meal or mate: Exploring the evidence of sexual cannibalism among amphibians - Gould - 2024 - Ecology and Evolution - Wiley Online Library

Figure 2
Adult female green and golden bell frogs, Litoria aurea, preying on adult spotted marsh frogs, Limnodynastes tasmaniensis in proximity to an exclusion fence on Kooragang Island, NSW, Australia. The females can be seen swallowing their frog prey vent first, with the back legs already consumed.

Gould, J., & Beranek, C. T. (2024). (CC BY 4.0)

Creationists who try to pretend to be the moral superior of other people like to pretend their imaginary creator friend has provided them with a set of objective morals, although bearing false witness to trick others into agreeing with them - something that their Bible says is wrong and something most honest people would agree with, seem to be one of them, as does abusing their opponents and even threatening strangers, as these are all part of the set of 'objective morals' on display in any on-line creationist or creation vs evolution group.

But even if the claim of there being a set of objective moral which their god has handed down to them (and only them) had any merit, you would expect it to be true for all species, not restricted to human cultures. After all, if eating people is wrong, then you would expect cannibalism to be unknown in the animal kingdom, and yet it's commonplace.

Which species are cannibalistic, especially during or after mating? Cannibalism, particularly during or after mating, is observed in several species across different animal groups. Here are some notable examples:

Insects and Arachnids

1. Praying Mantises: Female praying mantises are infamous for sometimes eating the males during or after mating. This behavior can increase the female's nutritional intake, benefiting her offspring.
2. Black Widow Spiders: Female black widow spiders occasionally consume the male after mating. The males often exhibit behaviors that try to prevent this, but it is not always successful.
3. Orb-Weaving Spiders: Similar to black widows, female orb-weaving spiders sometimes eat the males after mating.
4. Australian Redback Spiders: The male Australian redback spider offers itself to the female as a post-mating meal, which may increase the chances of successful fertilization.
5. Scorpions: Some scorpion species display cannibalistic behavior, especially when food is scarce. Mating can be a dangerous activity for males, as females might consume them after copulation.

Amphibians

1. Salamanders: Some species of salamanders exhibit cannibalistic behavior, particularly in larval stages. Larger larvae may eat smaller ones, especially when food is limited.

Fish

1. Guppies: In certain situations, guppies may exhibit cannibalism, particularly under crowded or stressful conditions. This can include eating their own fry.

Mammals

1. Hamsters: Female hamsters have been known to eat their young, especially if they are stressed, feel threatened, or if the young are weak or sickly.

Reptiles

1. Snakes: Some snake species, such as king cobras, are known to engage in cannibalism, often eating other snakes, including their own species.

Birds

1. Seagulls: Cannibalism in birds, including seagulls, can occur, especially in dense colonies where competition for resources is high.

Crustaceans

1. Crabs and Lobsters: Cannibalism is observed among various crustaceans, including crabs and lobsters. This can occur when individuals are molting and thus vulnerable.

Summary
Cannibalistic behavior, particularly during or after mating, often serves evolutionary purposes such as increasing nutritional intake for females, reducing competition, or as a result of environmental pressures. This behavior is more prevalent in species where the benefits to survival or reproductive success outweigh the risks.

But cannibalism is not restricted to a few arachnids such as black widow spiders who routinely eat their mate after he has served his purpose and mantises who do likewise, starting during copulation which continues without the male's head, which at that point is surplus to requirements.

Nor is cannibalism restricted to the female eating the male during or after mating but occurs in many species, especially when food is scarce, with many species consuming their own young, or one sibling consuming a smaller sibling. Several species of raptor begin incubating their eggs as soon as the first is laid, so the first may be a week or so old when the last is born. The youngest and smallest acts as a reserve food for the oldest when food is scarce.

UK viewers of BBC Spring Watch a couple of years ago may remember a tawny owl chick picking up its youngest sibling by the head and swallowing it whole on live TV, and a hen nightjar casually reaching round to consume her newly-hatched chick.

Now, all of this is intelligently designed, if you believe creationists, by the same god they claim gave them their superior 'objective' morals, and one particularly nasty examples of this amoral design was discovered recently amongst a species of Australian frog, the green and golden frog, Litoria aurea, where the (larger) female exploits the fact that a (smaller) male needs to emit a particular call to attract her.

This acts as a signal that there is a ready meal nearby, so, in trying to do what he was 'intelligently' [sic] designed to do, i.e., attract a mate in order to procreate, the hapless male signals that dinner is ready.

The evolutionary explanation for cannibalism in mating is that the male's body serves as nutrients for the developing eggs and embryos, so his demise benefits his, selfish, genes in a supreme act of altruism.

However, in the case of the green and golden frog, he doesn't even get to pass on his genes for them to benefit. He simply provides her with a meal that may ultimately benefit some other male's genes - and a male that in all probability avoided being eaten!

This discovery is the subject of a newly-published paper in the journal Ecology and Evolution by two researchers from the School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales, Australia.

Abstract
Active forms of cannibalism that involve predation of live conspecifics occur widely among amphibians, most notably by tadpoles that feed on each other and adults that feed on juveniles. In contrast, cannibalism among amphibian adults (adult–adult cannibalism) is less often reported and there have been no investigations on the occurrence of sexual cannibalism in this group to date. In this study, we present an observation of potential sexual cannibalism involving an adult female green and golden bell frog, Litoria aurea, preying on a conspecific adult male during the species' breeding season. By comparing our observation to the available literature, we show that adult–adult cannibalism among amphibians is rare but tends to be committed by females against their male counterparts. We thus suggest that the occurrence of sexual cannibalism should be extended to include this group, where sexual size dimorphism occurs widely among adults that congregate spatially during breeding periods, both predictors of intra-specific predation. We hypothesise that amphibian females may be able to exploit male advertisement calls to differentiate suitable partners from potential prey and that male individuals are vulnerable to sexual cannibalism as they must risk attracting and physically exposing themselves to females in order to reproduce. Our findings reveal the complex dynamics that exist within adult amphibian populations, suggesting that females may have a choice when deciding how to interact with and utilise their male counterparts. As our findings are preliminary, based on a small sample size of records, including several from captive individuals, we encourage authors to publish their observations of cannibalism in the field, including unsuccessful attempts, to confirm the presence of sexual cannibalism in this group.

1 INTRODUCTION
Cannibalism can involve active forms of intra-specific predation whereby individuals' prey on live conspecifics (Heinen & Abdella, 2005), which contrasts with the passive consumption (i.e., scavenging) of conspecific detritus/carrion. This is generally an opportunistic foraging strategy and occurs widely across animal groups (Fox, 1975; Polis, 1981). Adaptive benefits at the individual level include reductions in resource competition and provision of high-quality nutrients that lead to growth and development advantages (Meffe & Crump, 1987; Wildy et al., 1998), particularly during periods of food shortages (Amstrup et al., 2006). These benefits may be offset by associated costs including the risk of injury, disease transmission and reduced fitness by the killing of relatives (Crump, 1992; Fox, 1975; Pfennig, 1997; Williams & Hernández, 2006.1). At the population level, cannibalism may contribute to the regulation of population dynamics, including recruitment, population size and age structure (Fox, 1975; Hopkins et al., 2023; Polis, 1981; Whiteman & Wissinger, 2005.1) as well as dispersal (Rudolf et al., 2010). Identifying the presence and extent of cannibalism within populations may reveal complex interactions that exists between conspecifics that have been overlooked.

Among amphibians, active forms of cannibalism have been widely documented (Crump, 1992; Measey et al., 2015; Polis & Myers, 1985; Toledo et al., 2007), primarily involving adult life stages preying on juveniles, which have limited dispersal capacity, and unhatched embryos, which are immobile. This could be a strategy used by adults to reduce future competition or predation of their own offspring as younger conspecifics transition from being prey to a predator with increasing body size (i.e., status inversion; Kaplan & Sherman, 1980; Toledo et al., 2007). Cannibalism is also commonly exhibited by tadpoles that prey on conspecifics at the same life stage or unhatched embryos, including siblings (filial cannibalism) (Dugas et al., 2016; Gould et al., 2022). This may provide tadpoles fitness benefits by reducing competition for resources and increasing developmental rate, the latter being especially important for species that occupy ephemeral habitats where tadpole cannibalism is more commonly exhibited. Cannibalism is associated with situations where individuals are exposed to high population densities, low food resources and high levels of resource sharing (Fox, 1975; Polis, 1981). Among amphibians, this occurs under two main scenarios: when embryos hatch and large tadpole populations are rapidly exposed to limited resources and space (Gould et al., 2022) and when recently metamorphed juveniles make a transition from aquatic to terrestrial habitats that are used by adults (Measey et al., 2015). Yet, other concentrations of conspecifics also occur among amphibians, most notably the movement of reproductively active adults to breeding sites, including the formation of large and dense adult aggregations (e.g., Roberts, 1994), which should also provide suitable conditions for cannibalism to occur.

Yet, forms of cannibalism that involve adults preying on each other appear to be rare among amphibians, as noted by Muñoz Saravia et al. (2020). Indeed, in their review, Polis and Myers (1985) showed that adult–adult cannibalism accounted for few records in the literature, mirroring the low rate of its occurrence among other vertebrate groups including reptiles and mammals (Polis et al., 1984; Polis & Myers, 1985). This could be due to the negative effects of exploiting larger conspecifics as prey, including excessive handling times, reduced rate of success, reduced mobility upon digestion and increased risk of injury or death (Kaiser et al., 2016.1; Measey et al., 2015; Muñoz Saravia et al., 2020), despite the benefits of relatively higher nutrient intake.

Out of all forms of cannibalism, sexual cannibalism has received limited attention among amphibians (Elgar, 1992.1; Elgar & Schneider, 2004), despite species in this group commonly displaying sexual dimorphism and size disparity being a key predictor of intra-specific predation (Measey et al., 2015; Polis, 1981; Shine, 1979). During sexual cannibalism, adult individuals, typically females (but see Glaudas & Fuento, 2022.1), consume potential or actual mating partners; the most well-known examples being among predatory invertebrates (Elgar, 1992.1). Sexual cannibalism is considered a form of sexual conflict and may provide fitness benefits for the participating sex but also for preyed upon sex dependent on the timing of consumption relative to copulation (Zuk, 2016.2). For the participating sex, benefits include obtaining nutrients that can increase fecundity (adaptive foraging; Barry et al., 2008; Newman & Elgar, 1991) and preventing copulation with non-preferred mates (mate choice; Mark A Elgar & Nash, 1988; Persons & Uetz, 2005.2). For the preyed upon sex, it may increase fitness if consumption occurs after successful copulation, as the nutritional value provided to the mating partner may increase the chance of their offspring surviving (Buskirk et al., 1984.1). Unlike other forms of cannibalism, there is a relatively low risk of individuals who participate in sexual cannibalism killing close relatives. However, there may be negative population-level effects including reductions in population viability and extinction, particularly in the face of environmental change (Fisher et al., 2018), via the removal of available mates (Hurd et al., 1994.1). The potential for sexual cannibalism to occur among amphibians requires further investigation, including the conditions that may promote its occurrence and the consequences on adult population dynamics.

In this study, we present an observation of potential sexual cannibalism involving an adult female green and golden bell frog, Litoria aurea, preying on a conspecific adult male during the breeding season. We have subsequently reviewed the literature to explore the occurrence of adult–adult cannibalism among amphibians, including sexual cannibalism, and the conditions that may favour its occurrence in this group. For completeness, we test if there is a size-based sexual dimorphism present in L. aurea and if females were larger than males that they consumed when reported in the literature, which tests a key prediction of sexual cannibalism.

Video 1
Video recording of an adult Litoria aurea female cannibalising a conspecific adult male at the edge of a permanent wetland pond on Kooragang Island, NSW, Australia.

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Figure 4.
Time series showing an adult female green and golden bell frog, Litoria aurea, cannibalising an adult male at the edge of a permanent wetland pond on Kooragang Island, NSW, Australia. The female can be seen gripping the right hind limb of the male and dragging it down into a natural hole formation before the male escapes.

Gould, J., & Beranek, C. T. (2024).
Meal or mate: Exploring the evidence of sexual cannibalism among amphibians. Ecology and Evolution, 14, e11576. https://doi.org/10.1002/ece3.11576

Copyright: © [year] The authors.
Published by [publisher]. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

This illustrates how males and females can be on different evolutionary trajectories as it's obviously in the female's interest to eat males, especially those who don't measure up in terms of what she's looking for in her selection of a mate, but the males must balance the risk of being eaten against the benefit of passing his genes on to the next generation.

Unlike the arachnids which consume their mates after mating, where there is some benefit to the males genes in the trade-off between producing at least one batch of eggs, nourished by his own body, and the possibility of mating again, there is no such benefit to the male frog, apart from the small possibility that the eventually successful male may be a relative.

In terms of a supposed intelligent [sic] design by the giver of objective morals, as claimed by creationists, this is neither intelligent nor objectively moral, but then creationists must be getting used to the idea that their beloved god is a malevolent sadist with nothing resembling objective morals, unless objective morals are whatever a whimsical and capricious, sadistic monster does.

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