Summary in everyday language of recently published papers
Desert ants learn to reach food faster with experience but faster arrival to food does not depend only on learning
Learning can be defined as the improvement in the performance of a task with experience. The vast majority of animals can learn and insects are not different. Animals possessing a nest are typical candidates for studies on learning because they need to learn the way to food resources and back to their nest. Cataglyphis ants live in nests desert and Mediterranean areas. The ant workers that search for food do so individually and do not use trails. Therefore, each ant worker should learn the way to the food resource and back to the nest by itself. We examined whether and how fast Cataglyphis ants learn the way to an offered food resource while searching in an artificial maze in the lab. Maze-solving time improved dramatically already on the second trial and then remained constant and low. It takes the ant workers about 16 days to forget the way to the food reward and then maze-solving time returns to its original level prior to learning. We then asked whether the improvement in maze-solving time is indeed the product of learning the correct way in the maze. We discovered that ants solve the maze faster even without knowing the right way to the food and they do so when they are fed briefly before the experiment started. Our interpretation is that feeding them before the experiment makes the ants “believe” that food exists nearby, and then they solve the maze faster not because they know the exact way but only because they are more motivated to do so.
Read the related papers:
Saar et al. (2017) PLoS One
Bega et al. (2020) PLoS One
Learning can be defined as the improvement in the performance of a task with experience. The vast majority of animals can learn and insects are not different. Animals possessing a nest are typical candidates for studies on learning because they need to learn the way to food resources and back to their nest. Cataglyphis ants live in nests desert and Mediterranean areas. The ant workers that search for food do so individually and do not use trails. Therefore, each ant worker should learn the way to the food resource and back to the nest by itself. We examined whether and how fast Cataglyphis ants learn the way to an offered food resource while searching in an artificial maze in the lab. Maze-solving time improved dramatically already on the second trial and then remained constant and low. It takes the ant workers about 16 days to forget the way to the food reward and then maze-solving time returns to its original level prior to learning. We then asked whether the improvement in maze-solving time is indeed the product of learning the correct way in the maze. We discovered that ants solve the maze faster even without knowing the right way to the food and they do so when they are fed briefly before the experiment started. Our interpretation is that feeding them before the experiment makes the ants “believe” that food exists nearby, and then they solve the maze faster not because they know the exact way but only because they are more motivated to do so.
Read the related papers:
Saar et al. (2017) PLoS One
Bega et al. (2020) PLoS One
What are the best positions in a cluster of sit-and-wait predators and are small or large predators better at reaching such positions?
Not all predators chase after their prey but instead simply choose an ambush site and then sit and wait for prey to enter their detection range. Such predators usually live in clusters and are restricted to the type of area that provides the best conditions for ambush. In many of these clusters, the best positions are in the periphery, because prey arrive there first. Those predators in the central positions, therefore, catch less prey, as most prey are already intercepted by the predators in peripheral positions. Consequently, whether small or large, all predators should prefer peripheral locations in the cluster. It is common, nonetheless, to observe a difference in the positions within a cluster of small and large predators. A simulation model presented the spatial arrangement of such sit-and-wait predators. Small predators only occupied the cluster periphery under certain conditions, such as high prey abundance or low predator density. The reason is that such conditions moderate their need to frequently relocate, as too frequent relocation generally pushes the small predators away from the favorable peripheral positions. Large predators, in contrast, do not relocate so frequently, even when they are located in the cluster’s center, because they are able in any case to capture more prey than small predators. Moreover, any condition that triggers more relocation by large predators will bring them closer to the periphery. The model provides a possible mechanism for the distinct positions within the cluster of small and large predators. The model should be easily testable in systems of sit-and-wait predators, such as pit-building antlion larvae, which construct pit-traps in sand and ambush ants.
Read the related paper:
Scharf (2020) American Naturalist
Not all predators chase after their prey but instead simply choose an ambush site and then sit and wait for prey to enter their detection range. Such predators usually live in clusters and are restricted to the type of area that provides the best conditions for ambush. In many of these clusters, the best positions are in the periphery, because prey arrive there first. Those predators in the central positions, therefore, catch less prey, as most prey are already intercepted by the predators in peripheral positions. Consequently, whether small or large, all predators should prefer peripheral locations in the cluster. It is common, nonetheless, to observe a difference in the positions within a cluster of small and large predators. A simulation model presented the spatial arrangement of such sit-and-wait predators. Small predators only occupied the cluster periphery under certain conditions, such as high prey abundance or low predator density. The reason is that such conditions moderate their need to frequently relocate, as too frequent relocation generally pushes the small predators away from the favorable peripheral positions. Large predators, in contrast, do not relocate so frequently, even when they are located in the cluster’s center, because they are able in any case to capture more prey than small predators. Moreover, any condition that triggers more relocation by large predators will bring them closer to the periphery. The model provides a possible mechanism for the distinct positions within the cluster of small and large predators. The model should be easily testable in systems of sit-and-wait predators, such as pit-building antlion larvae, which construct pit-traps in sand and ambush ants.
Read the related paper:
Scharf (2020) American Naturalist
Is there a link between the habitat choice by wormlions and their success?
When animals choose to settle in some specific area or habitat, we assume they do it because it is in their best interests. This is usually true, but there are exceptions. Cities can provide such exceptions. All of us probably saw at least once a moth flying towards an artificial source of light, perceiving it by mistake as moonlight. In a series of experiments, we tested whether the habitats preferred by wormlions indeed provide them better conditions. Wormlions are maggots digging pit-traps in the sand and they always reside below a shade-providing shelter. Previous work emphasizes the importance of this shelter as a provider of shade. But what about protection against rain? Rain can be harmful to wormlions, as it destroys the pit-trap. We first checked whether wormlions prefer dry over wet small habitats in the lab when given a choice between the two. They do so in vast proportions of over 85%. After settling in and choosing a habitat, wormlions do not frequently move. The reason is the energy already invested in constructing a pit-trap. However, if we wet the pit-traps, wormlions abandon their habitat and move, searching for a dry one. Does this strong preference for dry habitats indeed translate to better performance in such habitats? The answer is yes. Wormlions in wet habitats cannot reconstruct their pit until the sand dries out. They also fail to capture prey. The reason is that ants can easily climb up a wet pit, as if it were a flat terrain, while they cannot escape a dry pit because they repeatedly fall inside.
Another example of this link between a preference for a specific habitat and performance is the preference for deep sand. Wormlions prefer deep sand over shallow sand when given a choice. They also construct larger pits in deep sand and more easily capture prey. Wormlions prefer fine sand or sand composed of small particles over coarse sand or sand composed of large particles. The reason for this is not yet clear, as we found little effect of sand particle size on pit dimensions or prey capture success despite the strong preference for fine sand. This preference is strong, and evident in nature, as sand collected from sites at which wormlions are present is finer and contains smaller particles than sand collected from adjacent sites, from which wormlions are absent. The reason for this preference for fine sand is still unclear, but might be detected somewhere else, such as easier maintenance of the pit-trap in fine sand.
Read the related papers:
Scharf et al. (2018) Animal Behaviour
Bar-Ziv et al. (2019) Current Zoology
When animals choose to settle in some specific area or habitat, we assume they do it because it is in their best interests. This is usually true, but there are exceptions. Cities can provide such exceptions. All of us probably saw at least once a moth flying towards an artificial source of light, perceiving it by mistake as moonlight. In a series of experiments, we tested whether the habitats preferred by wormlions indeed provide them better conditions. Wormlions are maggots digging pit-traps in the sand and they always reside below a shade-providing shelter. Previous work emphasizes the importance of this shelter as a provider of shade. But what about protection against rain? Rain can be harmful to wormlions, as it destroys the pit-trap. We first checked whether wormlions prefer dry over wet small habitats in the lab when given a choice between the two. They do so in vast proportions of over 85%. After settling in and choosing a habitat, wormlions do not frequently move. The reason is the energy already invested in constructing a pit-trap. However, if we wet the pit-traps, wormlions abandon their habitat and move, searching for a dry one. Does this strong preference for dry habitats indeed translate to better performance in such habitats? The answer is yes. Wormlions in wet habitats cannot reconstruct their pit until the sand dries out. They also fail to capture prey. The reason is that ants can easily climb up a wet pit, as if it were a flat terrain, while they cannot escape a dry pit because they repeatedly fall inside.
Another example of this link between a preference for a specific habitat and performance is the preference for deep sand. Wormlions prefer deep sand over shallow sand when given a choice. They also construct larger pits in deep sand and more easily capture prey. Wormlions prefer fine sand or sand composed of small particles over coarse sand or sand composed of large particles. The reason for this is not yet clear, as we found little effect of sand particle size on pit dimensions or prey capture success despite the strong preference for fine sand. This preference is strong, and evident in nature, as sand collected from sites at which wormlions are present is finer and contains smaller particles than sand collected from adjacent sites, from which wormlions are absent. The reason for this preference for fine sand is still unclear, but might be detected somewhere else, such as easier maintenance of the pit-trap in fine sand.
Read the related papers:
Scharf et al. (2018) Animal Behaviour
Bar-Ziv et al. (2019) Current Zoology
Wormlions like it dark. Do they consider also other factors in parallel?
There are different types of habitats on earth, but the fastest-growing ones are urban environments or cities. When choosing among several possible habitats to settle in, animals consider various characteristics of the habitat, such as the number of competitors and food abundance. Learning more about decision making while choosing where to settle, will help to predict which animals will not do well in cities and which ones respond to the opposite, by flourishing there. In addition to cats, pigeons, and cockroaches, cities in Israel are full of wormlions. Wormlions are small maggots or fly larvae that dig pit-traps in the sand in order to hunt other insects walking on the ground, such as ants. Moving insects do not see the pit-trap and fall into it. The wormlion grabs them and sucks their fluid content. Afterward, the wormlion throws away the corpse and waits for its next victim. In order to dig a pit, wormlions are satisfied with even a thin layer of sand. However, wormlions always construct their pits under shade. In the city, shade is induced by buildings while in nature wormlions occur in caves or below rocks. We believed that shade is important for wormlions because soils exposed to direct sunlight in summer can reach high temperatures, leading to desiccation and death. How could we test it? We first tested whether wormlions in the lab really prefer shade when given two options: shaded and lit small habitats. More than 80% of the wormlions chose the shade. But again, why did they choose shade? Is it indeed related to the high temperature expected to be encountered when choosing a lit habitat, exposed to direct sunlight? To answer this question, we repeated this small experiment in three temperatures: low, medium and high. If there is indeed a link between shade preference and temperature, the preference for shade should increase at high temperatures and should decrease at low temperatures. This is what our results tell us: wormlions’ preference for shade increased even more in high temperature, supporting the idea that shade preference is meant to avoid desiccation.
The world is not such a simple place, however, and wormlions do not only encounter shade vs. lit habitats. In addition to their shade preference, wormlions prefer also deep sand which is clear of obstacles, such as stones, and a habitat free of other wormlions that compete with them over space and potential prey. Disturbances, such as other individuals or stones lead to the construction of smaller pits, which result in smaller prey being captured and a higher chance for the prey to escape, even after it falls to the pit. This is undesirable from the wormlion’s perspective. How should a wormlion trade-off between these such conflicting demands? We thought that the effect of the absence of shade and of nearby competitors or obstacles is not symmetrical. In other words, the disadvantage induced by competitors nearby or obstacles on the sand leading to smaller constructed pits is negligible compared to the cost induced by the risk of desiccation and death. We tested it in a lab experiment by mixing these different constraints. Wormlions proved that we were wrong. If the preference for shade was over 80% when all other conditions were identical, it dropped to 60% when wormlion density increased in the shaded habitat or when the shaded habitat was combined with obstacles. Wormlions therefore consider several factors in parallel and perform complex-decision making while deciding where to settle and dig their pit-trap.
Read the related papers:
Katz et al. (2017) Behavioral Ecology & Sociobiology
Adar et al. (2016) Behavioral Ecology
There are different types of habitats on earth, but the fastest-growing ones are urban environments or cities. When choosing among several possible habitats to settle in, animals consider various characteristics of the habitat, such as the number of competitors and food abundance. Learning more about decision making while choosing where to settle, will help to predict which animals will not do well in cities and which ones respond to the opposite, by flourishing there. In addition to cats, pigeons, and cockroaches, cities in Israel are full of wormlions. Wormlions are small maggots or fly larvae that dig pit-traps in the sand in order to hunt other insects walking on the ground, such as ants. Moving insects do not see the pit-trap and fall into it. The wormlion grabs them and sucks their fluid content. Afterward, the wormlion throws away the corpse and waits for its next victim. In order to dig a pit, wormlions are satisfied with even a thin layer of sand. However, wormlions always construct their pits under shade. In the city, shade is induced by buildings while in nature wormlions occur in caves or below rocks. We believed that shade is important for wormlions because soils exposed to direct sunlight in summer can reach high temperatures, leading to desiccation and death. How could we test it? We first tested whether wormlions in the lab really prefer shade when given two options: shaded and lit small habitats. More than 80% of the wormlions chose the shade. But again, why did they choose shade? Is it indeed related to the high temperature expected to be encountered when choosing a lit habitat, exposed to direct sunlight? To answer this question, we repeated this small experiment in three temperatures: low, medium and high. If there is indeed a link between shade preference and temperature, the preference for shade should increase at high temperatures and should decrease at low temperatures. This is what our results tell us: wormlions’ preference for shade increased even more in high temperature, supporting the idea that shade preference is meant to avoid desiccation.
The world is not such a simple place, however, and wormlions do not only encounter shade vs. lit habitats. In addition to their shade preference, wormlions prefer also deep sand which is clear of obstacles, such as stones, and a habitat free of other wormlions that compete with them over space and potential prey. Disturbances, such as other individuals or stones lead to the construction of smaller pits, which result in smaller prey being captured and a higher chance for the prey to escape, even after it falls to the pit. This is undesirable from the wormlion’s perspective. How should a wormlion trade-off between these such conflicting demands? We thought that the effect of the absence of shade and of nearby competitors or obstacles is not symmetrical. In other words, the disadvantage induced by competitors nearby or obstacles on the sand leading to smaller constructed pits is negligible compared to the cost induced by the risk of desiccation and death. We tested it in a lab experiment by mixing these different constraints. Wormlions proved that we were wrong. If the preference for shade was over 80% when all other conditions were identical, it dropped to 60% when wormlion density increased in the shaded habitat or when the shaded habitat was combined with obstacles. Wormlions therefore consider several factors in parallel and perform complex-decision making while deciding where to settle and dig their pit-trap.
Read the related papers:
Katz et al. (2017) Behavioral Ecology & Sociobiology
Adar et al. (2016) Behavioral Ecology