Blue Tigers in the Mangroves

looking across mangroves to a bay
Mangroves at Cape Hillsborough National Park – looking south, with the boardwalk out of sight to the left

Back to Cape Hillsborough … the National Park is a peninsula and there’s a big area of mangroves on the broad, low-lying neck between the resort and the mainland. The “Diversity Boardwalk” loops through them and returns via higher ground to illustrate how land-forms shape plant communities.

boardwalk through mangrove forest
The beginning of the Diversity Boardwalk

All mangroves are salt-tolerant and don’t mind sand or wet feet but even within the family there is a variety of preferred habitats, and a small difference in height above sea level (even a metre or two) allows bigger mangrove species to thrive, so the boardwalk does earn its name. (Mangrove eco-systems are a huge topic in themselves – you could start with wikipedia if you want to explore them.)

But what about the Blue Tigers? Surely they should be even more famous than the Swamp Tigers of the Sundarbans? Sorry – they are butterflies.

Blue Tigers, Tirumala hamata, are Milkweed butterflies (Danaidae) like the Crows and they have the same habit of getting through the dry (winter) season by congregating in large groups in moist, shady places and doing as little as possible. I have seen groups of Crows on Townsville’s Town Common but was not at all prepared for the enormous flock of Tigers (flock?? cloud? school? flight? flutter? swarm? rabble? kaleidoscope??) I saw near the boardwalk car park.

blue butterflies on red flowers
Blue Tigers feeding on bottlebrush

I amused myself by seeing how many of them I could get into one photo, both in the shade and feeding in full sun on the flowering bottlebrush trees.

blue butterflies on trees
Blue Tigers resting in the shade

The beginning of October, when I saw them, was probably near the end of their resting season. There’s no sense in wasting energy making babies if they are going to starve as soon as they hatch, but as soon as the caterpillars’ food plants start growing again, normal life (i.e. breeding) resumes.

The Tigers weren’t the only butterflies enjoying the bottlebrush near the boardwalk that day; I also saw Wanderers, aka Monarchs (Danaus plexippus) and a Ulysses (Papilio ulysses) there. In the shade of the mangrove trail proper I saw Australian Rustics, Bush-browns and some unidentified Skippers. And I saw another, smaller, aggregation of Tigers on the Beachcomber Cove track, a little way up the hill from its resort end.

A friend in Townsville had this to say about Blue Tigers closer to home:

Blue Tigers … used to overwinter in quite large numbers along the track from Horseshoe Bay to Balding Bay [on Magnetic Island], quite possibly still do though they weren’t there when I walked the track on Saturday [early October], I think too late in the season for them.
Interesting that you saw them in Cape Hillsborough though – a bit cooler there perhaps?
… They are a favourite of mine. I’ve seen them overwintering in lowland vine forest in the Mission Beach/Kennedy Bay and Airlie Beach areas too, as well as the banks of Alligator Creek downstream from the swimming and picnic area – often they are with Crows, but the ones I remember seeing on Magnetic were exclusively, or almost exclusively, tigers.

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