Chasing the Elusive Tiger Swallowtails at Albany Hill

Albany Hill

In this post we go over our rather feeble attempts this year to tame the incredibly rare Western Tiger Swallowtail (Papilio rutulus). 

---

It is ironic that the Western Tiger Swallowtail (Papilio rutulus) was our first swallowtail, sitting so conspicuously on an apple tree (Malus domestica) in our very own backyard in the summer of 2012, even though it has since earned the status of being the most brutally difficult to find of all the local butterflies we have ever reared Albany. In these four years, we have only ever seen three of their caterpillars in real life including the one from 2012. Even the adult is a rare sight to see, only occasionally making an appearance in the city during their flight from May to June. This year, we still have not yet found a single egg or caterpillar nor have we been able to catch a live butterfly to lay the eggs for us, but we are actively trying!

Today we decided to try something new. Through careful observation over the last two years, we have come to the conclusion that the much more common Anise Swallowtail (Papilio zelicaon) is the only local swallowtail species capable of penetrating the urban environment. All other swallowtails are only abundant outside of the city, in parks and in the mountains. We speculated that Anise Swallowtails would also be rare if were not due to the widespread introduction of wild fennel (Foeniculum vulgare, a preferred host plant) but this can only be partly true since there are many of the Western Tiger's host plants available as well (however, we have yet to pinpoint exactly the particular host plants they most prefer and utilize in our region out of the many recorded ones). 

In any case, we went to Albany Hill where it borders Cerrito Creek in hopes that it would have a better yield than the city. Albany Hill is a natural area with a good amount of hiking trails and is a haven for native plants and wildlife, at least compared to the city. When we got there, we discovered it to be extremely dense in willow (near the riparian creek areas), live oak, alder, and bramble among some other commons. While we have only personally encountered Western Tiger caterpillars on apple (Malus domestica) and wild plum (Prunus), we trusted that they used some of the more typical host plants, especially willow (Salix). But even after about an hour of trekking the mountain, we were empty-handed. All we had saw were some small butterflies like Buckeyes (Junonia coenia), Cabbage Whites (Pieris rapae), Red Admirals (Vanessa atalanta), Mylitta Crescents (Phyciodes mylitta), and possibly some West Coast Ladies (Vanessa annabella). In addition, any eggs or caterpillars were simply too difficult to see up high in the trees and trying to find them where the host plant is so dense is like finding a needle in a haystack. 

However, when we were just able to leave near the bottom of the mountain, we spotted not one, but at least two adults fluttering gracefully in their natural habitat. We would never have seen so many in one day in the city, especially not at the same time. We knew immediately when we spotted them that they were not the much more common Anise Swallowtail due to their distinctly different wing shape, size, and pattern. In any case, a yellow swallowtail will more often than not be a Western Tiger rather than and Anise up in this typed of environment, especially since native umbellifers are uncommon on this particular mountain; like stated earlier, the mountains often are Western Tiger territory while the city is the Anise's. 

After another hour of struggling miserably to capture the beautiful butterflies in a futile game of cat and mouse while only equipped with a set of flimsy plastic cups and petri dishes, we eventually gave up. If we could have only captured a single female butterfly, we could end up raising a whole tub-full of caterpillars this year, but of course we did not. After today, we might seriously consider finally investing in proper butterfly-catching equipment such as a net. It may be well worth it, and not just for Western Tiger Swallowtails! In any case, we will definitely be back to Albany Hill sometime in future and hopefully it won't be too late to find anything then since the main flight is over starting in July. 

- Brian