Animal Behaviour

Wounded by love: snails struck by love darts have lower survival and reproductive rates

~ Betty ~ 4 Comments
"Shot through the heart and you're to blame, you give love a bad name" In this image of two mating snails, the snail on top shot a love dart through the head of its mating partner. (Credit: Chase and Blanchard, Proc. R. Soc. B (2006) 273, 1471–1475)
“Shot through the heart and you’re to blame, you give love a bad name” In this image of two mating snails, the snail on top shot a love dart through the head of its mating partner. (Credit: Chase and Blanchard, Proc. R. Soc. B 2006, 273:1471)

In classical mythology, Cupid carries two types of arrows: one with a sharp golden tip and one with a blunt tip made of lead. Those struck with the golden arrow are filled with uncontrollable desire while those wounded with the lead arrow are filled with revulsion. In these modern times, we humans are less likely to rely on a winged cherub carrying a quiver full of arrows to help us find love than on online dating sites and Tinder. That’s not to say that projectile weapon systems like the bow and arrow have become obsolete in affairs of the heart. Some species of land snails shoot love darts at their mating partners to increase their reproductive success.

As violent as it sounds, stabbing their mating partner with a love dart improves the likelihood that a snail will father offspring.  These sharp and pointy darts are made of a crystalline form of calcium carbonate called aragonite and coated with mucus. If the dart hits its target, chemicals in the mucus coating are released into the recipient snail’s blood stream. These chemicals serve as signals that trick the female reproductive organs to divert the shooter’s sperm away from the sperm digesting organs and into the sperm storage organs where they can fertilize eggs later. While love darts are known to carry clear benefits for the shooter, not a lot is known about how being hit by a love dart affects the recipient. For the first time, scientists have experimentally studied the costs of this violent and traumatic behaviour to the individual being stabbed. Continue reading →

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A case of magnetic attraction: sea turtles use magnetic coordinates to navigate to their nesting sites

~ Betty ~ 2 Comments

What do salmon, sea turtles and songbirds have in common? They are all excellent navigators capable of finding their way home after a long journey. These animals use a process called natal homing to make their way back to their birthplace to reproduce. Every two or three years, female sea turtles return to nest on the same beach where they first emerged as hatchlings. New research has shown that these turtles use the Earth’s magnetic field to guide them back home.

On a map of the world, you can pinpoint the exact location of any place using its unique latitude and longitude coordinates. Replace those latitude and longitude lines with intensity and inclination and you’ll have a new map of the world based on the Earth’s magnetic field. Inclination, the angle at which the magnetic field hits the Earth’s surface, and intensity are two important descriptors of the Earth’s magnetic field. Together, they can be used as a magnetic coordinate system, giving each place a unique magnetic signature.

Since the 1990s, biologists have known that sea turtles use the Earth’s magnetic field as a navigation system. One hypothesis in the field is that baby turtles imprint on the unique magnetic coordinates of their “home beach” as a way of guiding them back when they, themselves, are ready to nest. For the first time, researchers at the University of North Carolina, Chapel Hill have found evidence to support this idea of geomagnetic imprinting in sea turtles. Continue reading →

The Social Network: Why mama chimps behave differently with sons and daughters

~ Betty ~ 1 Comment

Ah, social skills. The curse of awkward teenagers everywhere and a key factor in determining the success of your upcoming blind date. As humans, we use our social skills to communicate and interact with others in both selfish and altruistic ways.

Like humans, chimps are highly social animals that live in communities. (Source)
Like humans, chimps are highly social animals that live in communities. (Source)

Chimpanzees, our closest living relative, also possess deft social skills. Adult male chimpanzees rely heavily on their social skills to form coalitions with other males to help them rise in the ranks and produce more offspring. On the other hand, female chimpanzee hierarchies are not determined based on strength and aggression, but rather, based on age. Females also spend a lot of time by themselves, nursing and taking care of their offspring. Are having good social skills, then, more important for male chimps than for female chimps? Would male infant chimps benefit more from having social interactions than females? Continue reading →