Identification of Invasive Species
The guttural trill is a sound that is pulled out from the throat often sounding harsh (“guttural”). For the Cane Toad, this goes on for thirty seconds and is also used when calling out to a mate (“Cane Toad”). One can see in video two a sample of the guttural trill from the Cane Toad. Also, Cane Toads are terrestrial when they become adults, but they are not terrestrial but aquatic when they are tadpoles. Terrestrial means that they are able to live on land. This is the process and the life cycle of the Cane Toad since it is an amphibious animal, which means that it is born in the water, but then it moves on as it grows to live on the land (“Bufo marinus (Linnaeus, 1758) - Cane Toad”). Figure 11 is a picture of a tadpole and figure 12 is a grown Cane Toad.
VIDEO 1 : How toads walk
VIDEO 2 : Guttural Trill
Physiological Characteristics:
First of all, the Cane Toad is an Amphibian, which means that it is a cold-blooded vertebrate, which can live both on the land and in the water (“Amphibian”). The average Cane Toad is about eleven to fifteen centimeters long. However, they can grow abnormally to about 23 centimeters and up to a kilogram in weight as well (“cane Toad”). There can be a variety of skin colors such as grey, yellow, or greenish brown with dry bumpy skin (Markula, Csurhes & Hannan-Jones). There is a difference in the female Cane Toads and the male Cane Toads as the female’s skin is much more smoother and they are bigger than the males (Markula, Csurhes & Hannan-Jones). This is because the Cane Toad is sexually dimorphic (Markula, Csurhes & Hannan-Jones), which means that behaviors and features vary between the different sexes of the species (Purves). Also, Cane Toads have glands behind their heads, which let out a poison, which can be lethal (Purves). Also, their Tympanum, which stands for the ear, is visible as well (“cane Toad”). There is some webbing on the toes of the Cane Toad and they don’t have suckers on their fingers or toes as well (“cane Toad”). One can see the Cane Toad labeled in Diagram 1.
For the toad eggs, they are not laid as separate eggs but they are laid as a chain, which is about 3 millimeters in thickness (“cane Toad”). When these eggs turn in to tadpoles, they are about 30mm and are of a black color (“cane Toad”). When these tadpoles turn in to metamorphs, which stand for new toads, they are about a centimeter long and not as quite as big as the average adult Cane Toad (“cane Toad”). The young toads, also called juveniles, have a pattern that helps them camouflage which is often a brown color, which can protect them from competitors (“cane Toad”). This pattern disappears as the Cane Toad gets older (“cane Toad”). One can see the cane toad life cycle as described in Diagram 2.
Behavioral Characteristics:
First of all, one of the behavioral characteristics of a Cane Toad is that they are mostly nocturnal which means that they are more active at the nighttime (“Cane Toad”). They often go searching for light in the night such as lamps because there are insects there, which could be eaten (“Cane Toad”). Also, another characteristic is how the Cane toads travel which is by walking and hopping. Toads do not leap and climb like many other frogs do (“Cane Toad”). One can see an example of this in video one. They are also different than frogs to the fact that when they sit, they often have better posture as they sit up straighter (“Cane Toad”). The Cane Toad also has a distinctive was of calling which is called the guttural trill (“Cane Toad”).
2) Niche:
- Space and Territory (Habitat): Cane Toads can be found in many different types of Habitats from sand dunes to rainforests (“Cane Toad”). They flourish the most in areas such as grass and woodlands (“Cane Toad”) that are moist and warm (“Cane toad (Bufo marinus, also Rhinella marina)”). However, they are able to survive in opposite conditions as well (“Cane toad (Bufo marinus, also Rhinella marina)”). They are a type of species, which is nomadic, which means that they do not have a habitat that is set in stone for them (“Cane toad (Bufo marinus, also Rhinella marina)”). Instead they move about 200m a day; the reason why they live a nomadic life is because of their skin as it is dry since it is not able to hold hydration like frogs are able to as they have a thin layer of a waxy material, which helps with this (“Cane toad (Bufo marinus, also Rhinella marina)”). Cane Toads only have the choice to change locations so they can get enough hydration thus having them change the locations every season (“Cane toad (Bufo marinus, also Rhinella marina)”). Cane Toads can survive with 50% of their hydration gone and they also can survive from temperature of five to forty degrees Celsius (Markula, Csurhes & Hannan-Jones). Also, Cane toads dig holes to create burrows where they are able to stay in the dry seasons and often use the same burrows again (“Cane toad (Bufo marinus, also Rhinella marina)”). Figure 13 helps visualize the burrows that the Cane Toads stay in.
- Interactions and relationships with other organisms: The cane toad does not have another relationship such as mutualism with other organism and only has the relationship of predation.
1) Prey of the Cane Toad (Predation): As mentioned in the nutrients section adult Cane frogs consume various different species ranging from insects like spiders, beetles to animals such as toads, frogs, and snakes to even mammals like birds and earthworms (“Cane Toad”). Tadpoles of Cane Toads consume their own kind as well which would go under cannibalism (“Cane toad tadpoles cannibalize their competitors”). One can see in figure 14, a cane toad consuming a mouse.
2) Predators of the Cane Toad (Predation): There are many predators of the Cane Toad as well. For example, there is the wolf spider; estuarine crocodiles, crows, water rats, and keel back snakes (Markula, Csurhes & Hannan-Jones). However, the Cane Toad is a difficult and dangerous resource to consume because as mentioned in the sections before, there is poison inside the cane toad, which is very deadly and toxic (Markula, Csurhes & Hannan-Jones). The only predator that can resist the poison of the Cane toad is the keel back snake, which is immune to this toxin and can survive with consuming it. However, since it takes a longer time to digest and has lower nutrition, it might not benefit the snake to consume this toad (Markula, Csurhes & Hannan-Jones). Also, birds like crows eat the frogs leaving out the poison glands as well (Markula, Csurhes & Hannan-Jones). Predators of the Tadpole’s include many different species such as tortoises, scorpions, leeches, and beetles. However, the biggest predator of the Tadpole is older juveniles or tadpoles (Markula, Csurhes & Hannan-Jones).
1) Features
- Nutrition and feeding Habits: The cane toad is an omnivorous predator, which will eat almost everything that they find edible (“Cane Toad”). Adult Cane Toads eat many different insects, which include spiders, termites, crickets, ants, and beetles (“Cane Toad”). They also eat aquatic species such as the marine snail, frogs, snakes, and even their own kind, toads (“Cane Toad”). They also are capable of eating mammals for example birds and are one example (“Cane Toad”). Cane toads have a huge appetite as they can eat up to two hundred foods in one day, which is more than many native species such as frogs (“Cane Toad”). Also, Tadpoles and juvenile Cane toads start cannibalism as well according to the University of Sydney and James Cook University (“Cane toad tadpoles cannibalize their competitors”). This is due to competitive reduction since they need the same habitat and the same resources, thus one tadpole is getting rid of the other in order for that tadpole to become a full-grown Cane Toad (“Cane toad tadpoles cannibalize their competitors”). In figure 13 one can see cannibalism going on between the tadpoles.
- Reproduction: Reproduction of Cane Toads start when they are about a centimeter long (Markula, Csurhes & Hannan-Jones). Breeding doesn’t have a set time but they are times and factors where it is most likely to happen (Markula, Csurhes & Hannan-Jones). For example, when it is warm and a hydrated weather breeding starts, thus, breeding starts in September for Australia since the weather is warm but hydrated (Markula, Csurhes & Hannan-Jones). In order for a tadpole to grow without it being stunted it needs to have a water temperature of 25 to 30 degrees Celsius (Markula, Csurhes & Hannan-Jones). Also, the ideal water is when it has a salinity of 15 percent and an alkaline pH compared to an acid pH (Markula, Csurhes & Hannan-Jones). The water has to be fairly shallow (Markula, Csurhes & Hannan-Jones). When the female Cane toads lay eggs they lay them in a chain format and about 8000 to 35,000 eggs are visible per chain (Markula, Csurhes & Hannan-Jones). In figure 15 one can see the chain of eggs from the Cane Toad.
3) Ability to outcompete local species
The Cane Toad has the ability to outcompete local species because of many different reasons and examples can be seen from comparing the native frogs of Australia and the Cane Toads. First of all, the main ability that the Cane Toad has to outcompete the local species is the toxin that it has. As mentioned before, Cane Toads have a toxin inside of them, which can poison the predators that try to consume them (“cane Toad”). These toxins can act as a competitive exclusion technique to outcompete local species. For example, many local frogs eat other tadpoles of different anurans, such as tadpoles and juveniles, including those of the Cane Toad (Shine). However, since the poison in the Cane toad is too strong for the frogs to take in, they would die (Shine). An example of this kind of frog species is called Litoria Dahlii, with the common name Dahl’s Aquatic Frog (Shine).
Another ability that the Cane Toad has that is used to outcompete local species is the fact that it reproduced much more rapidly than other local species. The Cane Toad produces 8000 to 35,000 eggs per chain and it doesn’t have a specific time period of reproduction except for a ride range that it is best in September (Markula, Csurhes & Hannan-Jones). Only 0.5% of these many eggs survive but that it still a lot of amount of toads that survive.as it is still about 175 toads (Markula, Csurhes & Hannan-Jones). Mass and rapid breeding causes the population of the Cane Toad to increase rapidly thus creating the toads to have competition with other local species.
The last ability that the Cane Toad has that is used to outcompete local species is that the Cane toad can consume anything in a great quantity. In the nutrition section, it was mentioned that Cane toads are predators and omnivores that can consume almost anything from small tiny species such as ants to large mammals such as birds (“Cane Toad”). They even consume their own species of Cane toads ever since they are a little tadpole (“Cane Toad”). Also, it was mentioned that they could eat two hundred foods in one day, which is a large amount of food for one day (“Cane Toad”). This will cause the food resources to run out due to the Cane Toads rapid consumption causing there to be a limit in resources for the local species who initially have to compete with the Cane Toads but cannot since the sources are all consume by the Cane Toads.