Solar Eclipses: When Day Turns to Night, How Do Sloths Respond?
On Saturday, 14 October, parts of the western hemisphere, including our little corner of the South Caribbean, will experience a breathtaking celestial show: an annular solar eclipse. The Moon will cover the Sun’s center during this event, revealing a radiant “ring of fire” or annulus around its perimeter.
There’s no denying the spellbinding allure of a solar eclipse. As the moon obscures the sun, day momentarily turns into night, and the world seems to stand still.
While humans don eye-protective glasses and flock to vista points with cameras in tow, the animal kingdom has its unique way of experiencing this celestial event.
How Wildlife Reacts to Solar Eclipses?
Solar eclipses bring about dramatic shifts in animal behavior worldwide. As the day momentarily darkens, diurnal animals, in their confusion, retreat to their nighttime habitats, while their nocturnal counterparts mistakenly believe it’s their time to emerge.

For instance, some orb weaver spiders, accustomed to dismantling their webs when night falls, start the process during the eclipse, only to rebuild once daylight swiftly returns. Diurnal fish and birds seek refuge in their usual nighttime spots, and the temporary darkness deceives bats. Notably, in Zimbabwe, hippos exited rivers during an eclipse, as usual at night.
However, as the eclipse’s shadow lifted and daylight returned, most of these animals returned to their usual day-time behaviors, while being noticeably disorientated for the rest of the day.
Sloths: Diurnal or nocturnal?
Before we delve into the impact of solar eclipses on these creatures, it’s essential to understand a sloth’s basic nature. Sloths are cathemeral and show little regularity or predictability in the hours they choose to be active, both within and between individuals.

How would an event as brief yet dramatic as a solar eclipse affect them? The honest answer is: we have no idea. However, given their photo-sensitive sight, it’s plausible to assume they’d have a noticeable response.
The Eclipse Moment: A Sloth’s Possible Reactions
- Momentary Wakefulness: If the eclipse occurs during their usual rest time, the sudden darkness might jolt them into a state of brief alertness. This reaction might be similar to how humans might wake up if someone suddenly turned off the lights in their room.
- Increase Movement: When the darkness arrives might feel the need to find a safer or more comfortable spot, mistaking the eclipse’s transient darkness for the onset of night.
- Looking Up: While many animals have been observed looking towards the sky during an eclipse, it’s unclear if sloths share this behavior. Given their unique perspective high in the trees and their natural curiosity, some sloths might tilt their heads upwards to the obscured sun.
- Resuming Normalcy: Since the total darkness of a solar eclipse is fleeting, any disruption in a sloth’s routine would likely be brief. They’d soon recognize the abnormality of the situation and revert to their regular activities.
Will we know how sloths react to solar eclipses?
While humans have the privilege of understanding and anticipating solar eclipses, animals, like sloths, experience them with unfiltered instincts and reactions.
One of our research goals through the Urban Sloth Project is to uncover whether the phases of the moon do indeed have an effect on sloth behavior. Luckily, during the month of October, we currently have six sloths equipped with Daily Data Loggers in the South Caribbean and three sloths at La Selva Biological Research Station.
During the average ten minutes that the solar eclipse will last, these devices will record hundreds of thousands of data points, including the sloths’ altitude and movement.
Through analyzing this data, we will be able to uncover if the solar eclipse event does have an effect on sloth behavior. So indeed, we’ll know exactly how they’ll react!
-Cecilia Pamich
Communications & Outreach