Animal Behavior: Videos & Practice Problems

Animal behavior encompasses the actions organisms take in response to stimuli, including interactions with their environment and other organisms. Behavioral ecology examines these behaviors, focusing on the ecological pressures that shape them. Within this field, researchers explore two primary types of causation: proximate and ultimate. Proximate causation investigates the mechanisms behind behaviors, such as genetic and neurological factors, while ultimate causation seeks to understand the evolutionary reasons for these behaviors and their impact on an organism's fitness.

For instance, consider the behavior of geese when an egg rolls out of their nest. This innate behavior, where the mother goose instinctively rolls the egg back, is triggered by the visual stimulus of the egg outside the nest. This behavior likely has deep evolutionary roots, possibly tracing back to ancestral species like dinosaurs. The fitness advantage is clear: returning the egg to the nest increases its chances of survival, thereby enhancing the likelihood of producing viable offspring.

Behaviors exist on a spectrum from learned to innate. Innate behaviors are genetically programmed and occur automatically, although some may require learning to refine certain aspects. A classic example of an innate behavior is yawning, which exhibits minimal variation across different organisms and is classified as a fixed action pattern. Fixed action patterns can be triggered by external cues known as sign stimuli. For example, male stickleback fish exhibit a fixed action pattern of aggression towards any object displaying a red belly, which serves as the sign stimulus. This response highlights how specific stimuli can elicit predictable behaviors, demonstrating the intricate relationship between behavior, environment, and evolutionary pressures.

Learning is fundamentally about acquiring or modifying behaviors based on experiences, often involving a choice that reflects a cost-benefit analysis. One intriguing aspect of learning is spatial learning, which allows organisms to create a mental representation of their environment, often referred to as a cognitive map. This concept can be illustrated through experiments like the water maze, where a mouse learns to navigate to a hidden platform using visual landmarks. Over time, the mouse develops a spatial memory that enables it to find the platform more efficiently in subsequent trials.

Another significant type of learning is imprinting, which occurs during a sensitive period in an animal's life, typically at a young age. During this time, an organism learns to recognize the characteristics of a specific stimulus, often a parent. For instance, ducklings imprint on their mother, following her based on learned stimuli such as appearance and sound. Interestingly, imprinting can sometimes lead to unusual behaviors, such as ducklings following humans or inanimate objects if they mistakenly identify them as their parent.

Communication among organisms involves the transmission and reception of signals, which can be chemical, visual, auditory, or olfactory. Pheromones are a prime example of chemical signals used by many species, including insects like bees, to convey information. A fascinating aspect of communication is the stimulus-response chain, exemplified in the courtship behavior of fruit flies. In this behavior, each signal sent by one organism acts as a stimulus for the next response from another, ultimately leading to mating.

However, not all communication is straightforward; some can be deceitful. For example, opossums may feign death as a survival tactic, demonstrating a form of deceptive communication. This type of communication is often more effective within a species, particularly in mating scenarios. In nature, some male animals may use deceitful tactics to gain access to females, such as disguising themselves as females to avoid detection by larger, dominant males. These behaviors highlight the complexity and sometimes humorous aspects of communication in the animal kingdom.

Mating behaviors encompass a range of activities aimed at attracting mates, competing for them, and caring for offspring. The structure of these behaviors is categorized into mating systems, with monogamy and polygamy being two primary examples. Monogamy is characterized by one male mating with one female, forming a long-term bond, as seen in albatrosses. In contrast, polygamy involves one individual mating with multiple partners of the opposite sex, which can manifest as either males mating with several females or females mating with several males.

Sexual selection is a specific type of natural selection where members of one sex choose their mates based on certain traits. This selection can be demonstrated through displays, such as the elaborate courtship rituals of birds of paradise, where females assess males based on their plumage and performance. These traits often serve as indirect indicators of the male's health and fitness. Additionally, competition among males, such as rams engaging in head-butting contests, is another aspect of sexual selection.

Mate choice copying is a fascinating behavior where individuals are influenced by the mating choices of others. For instance, in guppy populations, a female that observes a male mating with another female may be more inclined to mate with that male herself, highlighting the social dynamics of mate selection.

Parental care plays a crucial role in the survival of offspring, with males often participating in nurturing behaviors, especially in species that require significant parental investment. The certainty of paternity significantly influences male parental care; males are more likely to invest in offspring when they can be certain of their parentage. This is particularly evident in species with external fertilization, where males fertilize eggs directly, enhancing their confidence that the offspring are theirs. In contrast, internal fertilization can complicate paternity certainty, leading to varied levels of male involvement in parental care.

Overall, understanding these mating behaviors and systems provides insight into the evolutionary strategies that enhance reproductive success and the survival of species.

Animals often select their habitats based on the availability of food and mates, but some species engage in migration, which is the long-distance movement of populations typically linked to seasonal changes. Migration can occur for various reasons, including food availability, climate variations, and mating opportunities. There are three primary types of migration: piloting, which involves navigating using familiar landmarks; compass orientation, where animals move in a specific direction; and true navigation, which allows animals to find their way as if they were using a map. An example of true navigation is seen in sea turtles, which can sense the Earth's magnetic field to orient themselves accurately, even when disoriented.

Another fascinating behavior in the animal kingdom is altruism, which may seem counterintuitive as it involves a fitness cost to the individual performing the act, while the recipient benefits. This behavior can be explained through kin selection, an evolutionary strategy that enhances the reproductive success of an organism's relatives. Hamilton's rule provides a framework for understanding altruism, stating that altruistic behavior is more likely when the benefit to the recipient is high, the cost to the actor is low, and the coefficient of relatedness—representing the shared genetic material between individuals—is significant. This relationship can be expressed with the equation:

Benefit to recipient × Coefficient of relatedness > Cost to actor

Inclusive fitness expands the concept of fitness by considering not only the number of offspring an organism produces but also how it aids relatives in producing more offspring. This perspective suggests that altruistic behaviors, while not directly spreading an individual's genes, can still contribute to the propagation of shared genetic material among relatives.

Reciprocal altruism is another intriguing concept, occurring between unrelated individuals. In this scenario, an individual may temporarily lower its fitness to benefit another, with the expectation of future reciprocation. This behavior is observed in chimpanzee communities and may also shed light on human altruism.

A notable example of altruism is found in prairie dogs, which live in large communities with many relatives. When they detect a predator, they emit alarm calls to warn others, even though this behavior increases their own risk of predation. By alerting their community, prairie dogs enhance the survival chances of their relatives, thereby contributing to their inclusive fitness.