Trying to understand prickly pear/Tentando entender tuna

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In California, the prickly pears are now ripening, reminding me of something that confuses me: prickly pears protect their fruits the same way they protect their vegetation. In order for us humans to eat prickly pears, we must first remove the irritating spines. Now, I can see this as a deterrent to mammals – mammals have a long digestive tract which would destroy the seeds, so it makes sense for the cactus to defend its fruits from mammals. But then what? Reptiles? Don’t iguanas also have soft, fleshy moths that would be irritated by the spines? Birds? It is true that their beaks are hard like horn; but the little birds that peck pieces out of large fruits are not dexterous enough to remove such tiny spines. Wouldn’t they end up swallowing the spines and irritating their throats? What does the prickly pear disperser do to avoid the spines?

En California, las tunas ahora maduran, recordandome de algo que me confunde: nopaleras protegen sus frutas em la misma manera que su vegetación. Para nosotros seres humanos comer tunas, al primero tenemos que quitar las espinas irritantes. Bueno, puedo entender isto como dissuasorio para mamíferos – mamíferos tienen tracto digestivo largo, que destruiria las semillas, entonces tiene sentido para el cactus defender sus frutas contra mamíferos. Pero entonces, ¿qué? ¿Reptiles? ¿Iguanas también no tienen bocas suaves y carnosas, que estarán irritadas por las espinas? ¿Pájaros? Es verdad que sus picos son duros como cuerno; pero los pájaritos que pican pedacitos de frutas grandes no son tan diestros para quitar espinas tanto pequeñas. ¿No acabarian a tragar las espinas y irritar sus gargantas? ¿Que hace el dispersor de la tuna, para evitar las espinas?

If I recall correctly, and please call me out on this, at least some species drop the tiny spines on the fruit once they are fully ripe.

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When I’ve seen birds and lizards eating cactus fruit (prickly pear and other), they are careful to get at the fruit from between the clusters of spines. The make a hole, and eat from that. Sometimes I’ve seen them eat enough that a cluster of spines loses its support and simply falls off.

The spines aren’t evenly distributed all over the skin of the cactus and fruit, they’re in discrete bundles. As the fruit ripens the space between the bundles of spines increases, opening up access to the fruit. Think of drawing a bunch of dots on a balloon, then blowing it up. When the balloon is small you can’t touch it without also touching a dot, but when you blow it up there is space between the dots for your finger.

Galapagos iguanas eat prickly pear spines and all (even the big ones from the leaves), but they apparently often scrape them off with their front feet too. They, and some of the larger animals that eat cactus with the spines, like javalenas, have extremely tough, digestive systems that are well adapted to dealing with the spines.

Some animals rotate the spines as they eat thorny foods (eg. camels) so that they pass through the digestive system oriented lengthwise rather than horizontally, and with the thorns facing backward. This helps to keep the sharp ends from embedding until the digestive process can work its magic. With camels specifically, and their relatives, the llamas, alpacas, vicunas, and guanacos, they eat with a grinding motion that also helps to destroy spines and thorns. And yes, camels aren’t from areas where cactus are native, but prickly pear in particular is now widespread across the world and camels do eat it, along with thorny and spiny plants that are native to their regions.

With cactus specifically, many mammals eat cactus, but they’re generally careful to try to get at parts that have few spines.

Don’t underestimate how dextrous birds are with their beaks either, even small birds can do some extremely delicate work with their beaks.


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