I am interested in the complex relationship between animals’ eyes, their environment, and how they use color, shape, and movement to communicate with each other.
How best to catch her eyes? Attention-grabbing courtship in jumping spiders
How do we manage to stand out from the crowd when trying to communicate? The world is a visually complex place - there are always more things to look at, especially out in nature. Processing what we see takes a lot of brain power, so we can usually only focus on one thing at a time, and the same is true for animals. So, when an animal tries to send a message through a a courtship dance, or some other visual display, they have to first make sure that their audience is paying attention. Capturing attention is a problem that many animals need to solve, but we only know about how a select few manage to do so. I study how male jumping spiders attract the female’s attention during courtship.
In some species of jumping spiders, males perform elaborate courtship dances to impress a female - but how a female sees a males’ display depends on whether or not she is facing towards him! This is because some of a jumping spider’s eight eyes are better than others – the two biggest forward-facing eyes (“primary eyes”) see the sharpest image, while the others are much blurrier, but have a very wide field of view. The primary eyes are also the only ones that can see in color. So if a female turns away from a male, she can still see him, but his wonderfully colorful ornaments are now blurry and in monochrome!
How much of a problem is this for these spiders? We studied how male and female fiery-haired paradise jumpers (Habronattus pyrrithrix; native to the southwestern US and Mexico) positioned themselves during courtship. While males always directed their displays towards females, females often looked away from his dancing. In fact, females can see a male’s colors only 30% of the time! Since females are often looking elsewhere (perhaps watching for predators, or prey), males wait until females are watching intently before showing off their more impressive dance moves. This work was recently published in Behavioral Ecology (Echeverri et al. 2017) and covered by Popular Science.
We think that males have evolved ways to get females to turn around and face him. Males wave their front pair of legs back and forth when approaching a female - just like we might wave to someone from across a room! We are currently testing whether jumping spider waves work in the same way to get a female’s attention.
Color vision across the ages: Metamorphic changes in frog eyes
Do children and adults see color in the same way, and why or why not? How animals have evolved to see colors depends on what sort of things they need use their vision to do. Different animals have different lifestyles, and live in different places; different activities and environments make color vision more or less useful. So, as animals adapt to a new lifestyle, their color vision might change over a long period of time. But, many animals experience dramatic lifestyle changes throughout just an individual lifetime! Some frogs, for example, start off as herbivorous tadpoles living in murky water, and grow up to be predators hopping around on land. Each of these life stages might need different eye adaptations, but we don’t know very much about how such changes might affect color vision. What colors an individual can tell apart may depend on their age, and the same color might be perceived differently throughout a lifetime. I am beginning a project to understand how the photoreceptors in frogs’ eyes change as they metamorphose from tadpoles to adult. Whether or not color vision changes may depend on how big of a lifestyle shift a frog species experiences - frogs that remain aquatic as adults may have different changes than frogs that go from aquatic to terrestrial.