Ringed Planet: The shadow's effect on fauna

Question

I am writing a fantasy novel centered on an Earth-like planet with icy rings like Saturn. This question deals with certain effects of having such a ring system. Assume the planet is Earth, the rings are Saturn's rings (minus the C and D rings), and Saturn's ratio of planet/ring holds true for my planet.

On an Earth-like planet with rings, there would be a 'ring-shadow' constantly being cast somewhere on the planet. This shadow would only dissipate during the fall and spring equinoxes, at which point it would be centered on the equator, but be so thin as to not be noticeable. From the equinoxes to the solstices, the shadow would increase in width, and slowly travel towards the pole of whichever hemishere was experiencing winter. Further description of the ring-behavior can be found here, with pictures.

I don't think this shadow would fully block sunlight, but it would most likely resemble a total solar eclipse on steroids. Since no sunlight can get around the edges of the moon (because the 'moon' in this case is a ring completely covering the sun), light would necessarily be lower, though likely not at the level of night-time.

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This question deals with the effects of such ring-shadows on the local fauna. This is a fantasy novel, but assume there are no creatures besides what we already have here on Earth. I've looked at several articles on how animals react to eclipses, but they all have the same issue: the eclipse is temporary, and very out of the ordinary. The animals aren't used to it.

On a planet with a ring system, they would be used to it, as unless they live at the poles, the shadow would cross them at some point twice every year. How would fauna react to this?

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I realize any answer is going to draw heavily on speculation, but I want to make it clear that this question is NOT primarily opinion-based. Any theories or conjectures you come up with MUST be supported by evidence-backed logic, or at the very least have a clear logical deduction trail which can be traced back to observable fact. The best answer will be the one which details the most behavior changes/differences AND is the best backed/referenced by fact.

Answer 1

So, according to the Wikipedia page on Saturn's rings, and this handy "optical depth" to transmittance calculator I found, the amount of light blocked by Saturn's rings varies.

• C ring; ~12% - nearly transparant
• B Ring; ~60-100%, Structure varies heavily.
• A Ring; ~60-90% - Heavy overcast day?

Now - Saturn's rings are mainly water ice, with some dust. Therefore they couldn't exist around an earthlike planet as it would be too close to the sun, and they'd evaporate. For the purposes of this question though lets assume they're actually made of rocks and dust.

They're casting a pretty deep shadow on the planet below, although bands of sunlight do break through from time to time given the structure of the rings.

Assuming the rings are around the equator, and that the planet has a similar axial incline to Earth, this means the ring-shadow would occur during winter. The hemisphere that is closest to the sun at the time would be out of the direct line between the sun and the rungs, and receive normal light.

Based on that, I predict you'd see a much heavier reliance on the wintering strategies we already see here on Earth:

• Hibernation/Torpor
• Migration
• Food storage/hoarding
• Fat supplies
• Antifreeze blood (depending on temperature drop?)

Summer would be relatively normal, whilst winter is harsher than it already is. Most large animals would need to employ some sort of wintering strategy to ensure survival, perhaps more than one. Plants would likely use tubers to store nutrients.

The land near the equator would be even more prime real estate than it is now, because as you mentioned, besides the poles it's the only area not affected by the rings. Depending on the opacity of the rings, life may be strongly focused near the equator

Answer 2

I don't know that they would, at least not in an obvious, conscious way. The shadow will be pretty weak, lots of light will get past the thin layer of dust. It'll essentially be a season-long overcast day. Visual hunters may struggle a little more while in the shadow, since their prey will be able to hide better in low light. Herbivores may have a little more difficulty since the shadow will likely effect the length and quality of the growing season. This will be especially problematic if it coincides with summer. It'll be mostly irrelevant if the shadow coincides with winter. Some animals may use the shadow to time migrations or spawning.

Answer 3

Life on the planet would be very different.

To start, the planet would be colder on average as more light is reflected back into space.

The surface of the planet would be littered with craters, people would probably live in more fear of a meteor strike. There would be more dust in the air in general.

It's likely human development speed would be changed, both from the need for stronger houses from meteor strikes, and from the chance that someone like Newton could be the victim of an unlucky strike, setting back physics development.

You would see more northern plants under the ring. What us northerners call perennial flowers and evergreen trees as they are more suited to the colder temperatures.

Blue light deficiencies causing SAD would be more prevalent under the ring.

Gravity under the ring would be slightly different, possibly enough to create a tide.