Wow, it’s Wednesday again – that week went fast!
Apologies if last week’s blog post was a bit everywhere – that’s what happens when I try and write an overview of bats but also not write a small novel at the same time. Today’s post will be much more to a point and will be an overview on a group of bats very close to my heart: the tent-making bats.
It always blows my mind that many people I’ve met don’t know about these funky critters. I honestly think they should be up there with all the main animals people think of*. Put simply, these are bats that chew leaves to make tiny houses to live in! HOW ADORABLE IS THAT?! Phew… ok explosion over… but seriously, incredible, right?
* – I think that about all bats, but I have to compromise somewhere…
There are 22 documented species of bat that make tents1, some of these bats are obligate tent roosters* (e.g. the Honduran white bat, Ectophylla alba2) whereas others can be found in different roosts as well, such as caves and trees (e.g. the Jamaican fruit-eating bat, Artibeus jamaicensis3). They are only found in the paleotropics (tropical Africa, Asia and Oceania) and the neotropics (Central and South America). There are many different shapes of tent such as pinnate, apical, conical, boat and palmate umbrella to name but a few (see pictures)4. Some bats, like the Honduran white bat, will only make one kind of tent out of a fairly restricted number of plant species†4. Others are masters of flexibility and use a whole range of plants to make many different shaped tents, such as the Thomas’ fruit-eating bat (Dermanura watsoni‡)4. The bats make the tents by chewing carefully, avoiding any important plant tubes. The result is that the leaf remains alive whilst the bats live inside, and some tents can even last up to 9 months5. It’s quite dependent on the plant species, though, as tents made in Musa spp. only last for under a month6. I guess because some leaves go mouldy quicker.
* – Only make, and roost in, tents
† – Boat tents in mostly Heliconia and Musa spp.4 if you’re interested!
‡ – Sometimes called Artibeus watsoni in earlier research
So why do they make these tents? Pretty much for the same reasons we build houses! Tents provide the bats with shelter from rain, wind and sun, as well as some protection from predators7. Tents also have the added quality of being quite ephemeral*. Unlike cave-roosting bats, tent-making bats can switch roost position frequently, preventing accumulation of ectoparasites8†. There was some hype in the 90’s based on a single observation of a male bat making a tent. Ideas were drawn up about males making tents as a means of attracting females, and nice tents being defended by males4,5,9. I got very excited about this and wrote a short journal article on it in my first year of uni (available here: https://exestem.files.wordpress.com/2018/11/undergraduate-science-volume-2-issue-1-march-2018.pdf) but there are a few reasons why the theory is unlikely to be the case…
* – Ephemeral: fleeting, brief, here for a moment and then gone the next, tents go mouldy after a while whereas caves don’t etc… Undoubtedly one of my favourite words!
† – Ectoparasites are parasites on the surface of the bats; things like ticks and bat flies. If bats hang around in the same spot for a long time, in theory, more parasites will find them.
Firstly, as mentioned, bat tents are very ephemeral. If a males bat’s reproductive success (how many girlfriends he manages to pull) depends on the quality of the tent he makes, then he’s only got a fairly short time to get his game on – making it quite unlikely this is the case10. Furthermore, when I went out to Honduras to see these bats for myself, I found loads of tents used by just a few bats*. A male would therefore have to defend a large number of tents in his territory, which is tricky and impractical. Some of these tents would lose condition faster than others and potentially compromise his reproductive success if a mouldy tent dissuades the females. Finally, scientists have also now observed a female building a tent11, so it’s not just a guy thing. That was sort of the nail in the coffin for that idea, but hey – I got a small published review paper from it so I’m happy!
* – Interestingly, bats would use these extra tents as escape shelters if accidentally disturbed; for example, by one of my volunteer research assistants suddenly blasting ‘Titanium’ by David Guetta in the middle of data collection in the Honduran swamp forest… Words fail me.
And that brings me on to the coolest thing about tent-making bats – we really don’t know much about them. How often do they make tents? How long does it take them? Is it a team effort or just one bat? Do they learn to make tents from each other, or is it innate? We just don’t know! It’s odd because usually funky behaviour like this gets a lot of scientific attention, but sometimes even the most charismatic animals can get overlooked. I have heard of only three observations of tent-making behaviour, and only 2 of those were direct11,12. It’d be awesome to just go out there and find out the answers, but funding is hard to come by, and usually requires a precise reason why the research is being done. Sadly ‘because it’s cool’ doesn’t count!
I thought I’d end on an example of some excellent early-scientist sass. Anyone who’s read some old science papers will know that scientists were often quite rude to each other if their ideas conflicted. One of the very first scientists to describe tent-making bat behaviour had a hard time convincing his peers that the bats made the tents, not some insect species13. He ends his 1932 paper with the fabulous quote:
“I sent some of the leaves to my doubting friend Miller and when I saw him in Washington a few days ago he admitted in moderation that it looked now a little as if I might be right after all. I rather think so too.”
- Rodríguez-Herrera et al. 2007 | ISBN: 9968-927-28-4
- Rodríguez-Herrera et al. 2008 | DOI: 10.3161/150811008X331126
- Ortega & Castro-Arellano 2001 | DOI: 10.2307/0.662.1
- Kunz et al. 1994 | DOI: 10.1007/BF01464350
- Kunz & McCracken 1996 | DOI: 10.1017/S0266467400009342
- Chaverri & Kunz 2006 | DOI: 10.1111/j.1744-7429.2006.00107.x
- Foster & Timm 1976 | DOI: 10.2307/2989720
- Lewis 1995 | DOI: 10.2307/1382357
- Tan et al. 1997 | DOI: 10.1080/00222939700770861
- Adams et al. 2017 | As yet unpublished (available here: https://science.umd.edu/faculty/wilkinson/Adamsetal2017.pdf)
- Rodríguez-Herrera et al. 2006 | DOI: 10.3161/1733-5329(2006)8[557:TBBFEA]2.0.CO;2
- Balasingh et al. 1995 | DOI: 10.1111/j.1439-0310.1995.tb00326.x
- Barbour 1932 | DOI: 10.1086/394410
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