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  • Amazing Facts About Frogs

    Amazing Facts About Frogs

  • Tarantulas Have Animal Friends

    Tarantulas Have Animal Friends

    Better than their reputation: While tarantulas cause fear and rapid heartbeats in many people, biologists have discovered that they are surprisingly popular in the animal kingdom. According to research, these eight-legged hunters maintain symbiotic relationships with a variety of other animals — especially toads and frogs, but possibly also with other spiders and even snakes, termites, and ants. Interestingly, these relationships of tarantulas could also explain why they are so hairy.

    Fear of spiders is one of the most commonly cited phobias. Encountering a tarantula (Theraphosidae) with its ten-centimeter-large, hairy body in real life would probably be an absolute nightmare for many people. However, these eight-legged hunters pose no real danger unless you’re a cockroach or grasshopper. Tarantulas are also not averse to small mammals and snakes if they manage to overpower them.

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    Friendly Spider Seeks Croaking Roommate

    But tarantulas don’t just spread fear and terror in the animal kingdom. There are repeated reports of cases where these eight-legged creatures form close relationships and even symbioses with animals of other species, such as frogs and toads, even sharing their burrows with them. Alireza Zamani from the University of Turku in Finland and his team have now investigated how widespread such phenomena are. As part of a comprehensive literature review, they collected all known observations of tarantula symbioses and analyzed them in a review paper.

    The results showed that symbioses with frogs and toads alone, which are collectively known as anurans, have been observed 83 times in tarantulas across 17 countries. “Most of these observations describe the presence of more than one anuran individual either at the entrance or within an occupied terrestrial burrow of a tarantula,” report Zamani and his colleagues. The frogs and toads apparently lived there together with the spider and were not attacked by it.

    Win-win in the Shared Living Space

    “Obviously, the frogs and toads living in the tarantulas’ shelters benefit from protection against their predators,” explains Zamani. In an experiment from 1980, a tarantula even protected its amphibian roommates from a dangerous snake. But what does the spider gain from this arrangement?

    The frogs and toads that the spider allows to live with it feed on insects. These insects, in turn, can be dangerous to the eight-legged hunter itself, but especially to its eggs and young, as the researchers explain. “Anurans offer protection particularly against parasitic flies and predatory ants,” the team writes. Thus, both sides and their offspring benefit equally from this unusual shared living arrangement.

    Diverse Roommates

    But tarantulas don’t just open their doors to amphibians. As Zamani and his colleagues have discovered, there are also 14 known cases where they shared their burrow with smaller spiders such as harvestmen and whip spiders. However, it’s still unclear to what extent the roommates benefit in each case. The same applies to three cases where a snake was observed in the spider’s burrow without any attacks occurring.

    In some places, termites and dangerous army ants also come and go in the tarantulas’ burrows. These are actually known for attacking and eating a variety of arthropods. However, they usually spare the tarantulas and their young, as the collected observations suggest. They probably only help themselves to the remains of the eight-legged creatures’ last meals in the burrow and, as a side effect, give it a thorough “cleaning”, which also benefits the spider.

    Mystery of Spider Hairs Solved

    The cleaning crews in the spider’s burrow are not completely harmless, though. Individual ants occasionally attack the spider itself, despite the abundance of food remains, but they never get far, as Zamani explains: “The dense hair covering the tarantula’s body makes it difficult for ants to bite or sting the spider. Therefore, we believe that the hairiness might have evolved as a defense mechanism.

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    ” For this reason, some tarantulas probably also cover their egg sacs with urticating hairs.

    In addition to their hairs, tarantulas might also use a defensive secretion to protect themselves, the researchers suspect.

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    “This hypothesis is supported by the observation that cats and dogs, animals with a highly developed sense of smell, tend to flinch and move away when they sniff a tarantula,” says Zamani. However, solid scientific evidence for this chemical defense is still lacking.

  • How Frogs Catch and Swallow Their Prey

    How Frogs Catch and Swallow Their Prey

    Frogs have to remove insects like flies and crickets from their sticky tongues before they can ingest them. The process by which cane toads accomplish this feat has recently been determined by scientists. As the research shows, sophisticated tongue gymnastics are necessary to get the victim far enough into the pharynx to be gutted. The hyoid bone, which has never before been linked to swallowing, is also crucial.

    Frogs will stick their lengthy tongues out of their mouths while pursuing flying insects. Insects often attach to this and then fall into the amphibian’s mouth if the strategy is successful. The specifics of how frogs extend their tongues and utilize them to grab prey have been studied extensively. Studies have shown, for instance, that frog tongues are not sticky until they are in touch with food.

    However, according to Rachel Keeffe of Mount Holyoke College, whose team has investigated what occurs following prey acquisition, almost everything that occurs after the mouth shuts has remained a mystery.

    What’s Happening Inside

    How Frogs Catch and Swallow Their Prey

    Keeffe and her colleagues videotaped cane toads eating to get insight into the process by which frogs remove food from their tongues before swallowing it. Because of their size (cane toads may grow to be as long as 5.9 inches or 15 cm), the inside workings of their mouths are easily studied. Keeffe and her colleagues kept the animals in a Plexiglas enclosure and fed them crickets during the research.

    The tongues of cane toads can grow to be as long as 80% of their heads.

    They used a high-speed camera and X-ray footage to capture the action on film. They were able to see what was happening inside the toads. Metal beads were placed in strategic places in the toads’ mouths to enhance the visibility of the necessary structures under X-ray.

    The resultant video material was then recreated by Keeffe into 3D animations so he could examine the movement patterns more closely. She used the animations to create a detailed flow chart that describes the whole feeding cycle of a cane toad, from the time it first spots the cricket until the time it dies in the toad’s stomach and the toad returns to its original condition.

    The Hyoid Retracts Into the Neck

    The results surprised researchers because they revealed a more complex system than anyone had imagined for how a frog prepares its prey before placing it in its throat. The hyoid bone plays a crucial role in this system. The frog’s tongue is attached to the hyoid bone, a cartilaginous plate located near the floor of the mouth. When the frog lunges at its target with its tongue, the hyoid bone retracts into the neck, bringing the tongue and prey back into the mouth.

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    toad tongue hyoid
    Some of the hyoid muscles, seen here with the tongue outstretched. The color blue describes the hyoid cartilage. (Credit: Oxford Academic)

    Records have shown that during this recovery movement, the tongue moves much further into the throat than during prey capture. This process involves a network of cartilage and muscle that extends so far back in the frog’s throat that it touches the organ that pumps blood throughout the body. The next movement involves the tongue bone thrusting forward, causing the tongue to be pushed against the hard palate of the mouth and pulled back from the pharynx.

    In this way, the esophagus encloses the prey that is stuck to the tongue. Keeffe thinks that frogs’ palatal grooves, or extra rows of teeth, help with the frictional action necessary to remove prey from the frogs’ sticky tongues. This is a very interesting development, considering that until this discovery, the purpose of the grooves and small teeth was a mystery. He also mentions the hyoid bone, which was not previously linked to swallowing.

    It Takes Less Than Two Seconds

    It takes less than two seconds for the toad to go from seeing the cricket to its original form. This is still far longer than was anticipated. The time it takes to acquire prey is much less than two seconds.

    It was also intriguing to see the toad’s intricate swallowing process in action, both when it successfully caught the cricket and when it failed to do so.

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    In any event, experts believe that the toad’s tongue has to make its way back down the throat before it can start a new feeding cycle.
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    Keeffe suggests that future studies should investigate whether or not the swallowing technique of cane toads is shared by other frogs, or whether or not they use other methods of digestion.

  • Can Frogs Really Predict the Weather?

    Can Frogs Really Predict the Weather?

    Frogs are weather experts. Some frogs and toads, based on their croaking, egg-laying, and even skin color, are said to allow us to predict whether it will rain soon or not. But what is the truth behind the frogs’ purportedly preternatural weather forecasting abilities?

    Long ago in Switzerland, if you would put a tree frog in a jar half full of water and give it a little ladder to climb, it could forecast good weather by climbing the ladder and bad weather by descending back into the water. Even today, in Germany, a weatherman is referred to as a Wetterfrosch, which translates as “weather frog.”

    Tree frogs are known to climb trees in favorable weather and make an awful noise, croaking sweetly for hours on end, thus the frog weather prediction theory actually has some validity.

    Monitoring the Humidity

    Numerous accounts point out the daily behavioral changes in amphibians and some reptiles related to predicted weather. Some species, for instance, become more active just before it starts to rain, while others are more likely to make their distinctive croaking sounds. The weather probably has a lot to do with this shift in behavior.

    Frogs and toads are highly reliant on accurately monitoring the humidity or temperature of their surroundings. That’s because amphibians are ectothermic, meaning they don’t produce their own heat. So, their blood, muscles, and skin, along with the rest of their organs, are always at the same temperature as their surroundings.

    Exceptionally Sensitive to Moisture Levels

    Frogs’ skin is very porous because of the abundance of glands on its surface. Because of this, they suffer significant water loss due to evaporation. But frogs and toads have a more refined sense of moisture via their skin than people do. In the tropics, for example, certain frog species usually come out of the underbrush when the humidity rises in anticipation of rain.

    Finally, amphibians like frogs and toads produce their offspring in aquatic environments. Thus, in order to effectively reproduce, they have to predict when there will be adequate puddles and pools from rain in which their tadpoles may grow. This means that when the weather or temperature changes, frogs have to adjust their behavior accordingly.

    Climbing Tree Frog

    So why then do frogs choose to remain low when bad weather is approaching, yet climb up when conditions are favorable? There are no precise investigations of the topic available. However, there are two theories among frog scientists as to why this occurs: The tree frog, in contrast to most other frog species, enjoys vertical environments and bright sunlight. Male frogs, especially those still in their juvenile stages, spend most of the late summer sitting on bushy branches and leaves to soak up some rays.

    However, the accessibility of food is equally important. The same goes for tree frogs, who also utilize their perches to swoop down on prey. Insects like mosquitoes are sensitive to weather changes, something our ancestors accounted for in their agricultural guidelines. With less wind and more sunshine, insects may ride the warm updrafts to greater heights in their flights. They tend to linger on the ground if a severe wind and a drop in temperature are expected.

    It is unknown, however, whether tree frogs actively pursue prey higher or lower, or if they instead respond immediately to changes in the weather. One thing scientists can agree on is that frogs and toads frequently respond to a shift in the weather before humans do. And this, of course, has nothing to do with clairvoyance.