Is this a viable/realistic imaginary species?

Question

I am creating a species for my alien world that will be seen as 'holy' by the planets dominant religion. I'd like to know if my 'holy' species could viably exist biologically/evolutionarily.

Assume that the alien planet has the same general physical properties as ours, the only difference being a higher oxygen content and slightly less gravity.

The species is a marsupial, slightly larger in size than a above average capybara. It is a herbivore and has raccoon like hands with opposable thumbs.

Here is the part where it becomes alien: the females of the species have large downward curving horns on either side of its head, like a ram, but flatter and concave. They use these to scoop up soil and plant life and then grow them in the horns. This is like an emergency supply of food for their young encase there is none around them.

Specifically the type of soil/plant they scrape up into their horns would be ground racing berry plants like strawberries. These berries would actually ripen and grow quicker in their horns because of a hormone that the species produces called ethylene which promotes the ripening of fruit. This is the reason the dominant religion on the planet thinks they are holy as they use 'magic' although it isn't really.

The male of the species also have horns but do not produce the hormone and their horns are frontward facing and used for fighting/mating purposes.

So is this a realistic species that could have evolved?

Some points I'm worried about being unrealistic:

• A mammal producing a hormone like ethylene.
• A species' male and female having very different horns.
• The viability of the plants being able to grow after being uprooted. (Perhaps they would need to just be soil with the seeds in it but not grown yet?)

Answer 1

I like it.

There is no reason a berry plant could not grow in a small pot. So there is no reason it could not grow in a horn. The soil would leach nitrogen from the horn; keratin (usually hair, but why not horn)is good mulch for this reason.

Sexual dimorphism: if horn is for a purpose unrelated to gender females and males can both have horns. Male and female cape buffalo have similar horns because they are for fighting predators, not conspecifics. So your berry pot horns can be on males and females both.

My one change: the berry is not for food. You could not grow enough calories in a horn to make a difference for an animal big enough to carry around the horn. The berry makes vitamins. I could carry around a pot big enough to grow enough scurvygrass to prevent myself from getting vitamin C deficient. So too your creatures: their diet and environment is low in a given vitamin they need but the berry makes that in abundance.

The berries carried by the animals make much more vitamin than the wild version does. Animals with high vitamin berries do better and have stronger offspring. Those offspring get runners of the berries of their parents. Over time mutual selection favors super berries.

Answer 2

There is a major problem with this species: a plant needs nutrients to grow. Not just sunshine and CO2, but water, minerals, proteins etc. Normally, those would be acquired from the soil and/or from symbiont microorganisms. If, instead, those nutrients come from the carrying animal, then the carrying animal is expending precious energy and resources now, for a "just-in-case" later scenario.

There are also a number of smaller problems.

• Plants require sunlight. Is your animal diurnal? Even if it is, does it favour open spaces (as opposed to being under trees)? Does it have no need to hide from predators?
• Having plants to the side of the animal's face would significantly constrict it's field of view, making it considerably harder for it to hunt/scavenge for food, avoid predators etc. It would be like a horse wearing blinkers.
• The extra weight of the plant would add to the energy the animal must expend to sustain it. Also, it would shift the animal's centre of mass, potentially off-balancing it.
• For a plant to produce fruit, it needs a considerable amount of water and nutrients, A starving plant will not produce fruit. So, in a period of starvation, your animal would be sustaining a plant, giving it more energy than it would receive back from the fruit.

A plant-animal symbiosis is possible, but the animal needs to benefit from it all the time, not only in edge cases. Otherwise, the costs outweigh the benefits.

Answer 3

I would go with:

Grow - no
Ripen - yes

Indeed, the ripening could be an example of mutualistic evolution - the plant gains something from the animals' carrying of the fruit (perhaps the fruit sheds seeds gradually as the animal walks around) whilst the animal gets the fruit to ripen and make it much more palatable to eat.

But it's hard to imagine fruit growing much - although it is theoretically possible; the fruit could photosynthesise and draw chemicals from the atmosphere.