Cross-Pollination: First Bat Monitoring: A Tale of Frozen Batteries and Beautiful Scenery

First infrared bat monitoring and agave survey: done! Earlier this week I traveled with Claudia, Temo, Gehu, and Isra to Tepozanes and El Refugio, two ejidos in southern Nuevo Leon about six hours south of Monterrey. This year ESHAC is doing a community-based project to develop community and individual organic gardens for produce and other useful plants in several communities in Nuevo Leon and Coahuila, and I am going along on most of their trips to do my own work with the communities (doing group discussions and individual interviews (household surveys) about agave uses and harvest) and with the bats and agaves (doing infrared camera monitoring of flowering agaves to measure bat foraging and doing agave surveys).

While Tepozanes and El Refugio are not near current known roosting caves of Mexican long-nosed bats and are therefore not my “top” priority sites for my research, these locations are still worthwhile to visit and do my work, for several reasons. First, there are caves and mines in the area and historical records from the 1960s and later of Mexican long-nosed bats in these caves/mines. Second, these communities are in the southern part of the mountain range that Mexican long-nosed bats likely migrate through on their way to the known roosting caves farther north, and therefore working with communities in these areas (that have many agaves) to investigate the potential for “bat-friendly” management is worthwhile to pursue. Third, there is another species of bat that feeds on agaves (the Mexican long-tongued bat, Choeronycteris mexicana) that is found in the area and is listed as Threatened by the Mexican federal government and Near Threatened by the IUCN, so any conservation work for my target species (the endangered Mexican long-nosed bat) in this area will benefit this species too. Finally, given the limitations of my current funding and the logistics of traveling here (aka needing a field vehicle and needing to go with others and not by myself), at least for this year it is necessary for me to coordinate/coincide trips with ESHAC’s trips, and Tepozanes/El Refugio is one of their project sites this year.

The drive to these communities is not too treacherous (not nearly as nerve-wracking as the narrow windy dirt road through steep mountains to Infierno Cave that we took on a trip last summer!) although the windy mountain roads were making my stomach a very wee bit upset. But the scenery is beautiful!

A beautiful natural wetland near the town of Zaragoza

(in southern Nuevo Leon) where we stopped to look for flowering agaves

Mules grazing in Ejido El Refugio (southern Nuevo Leon),

with some agaves nearby

A paniculate agave (aka an agave with numerous umbels (groups of flowers)

branching from the center stalk) in full flower outside El Refugio. The bat I’m

studying feeds on these the nectar and pollen of these flowers.

The communities in this region often plant agaves in rows along fences,

presumably for erosion control and/or ornamental purposes. During my focus

groups and interviews with communities I will be asking them about these uses

of agaves (among other uses) to understand the potential for incorporating

“bat-friendly” agave use in these communities.

We arrived around 5:00pm and visited with several people that Claudi and the rest know from their previous work in the communities. We also drove around scouting for flowering agaves where I could set my infrared monitoring system up. There were many agaves dotting the hillsides and near the small houses of the communities, but only a handful in flower. Most were either too young to flower this year (agaves have semelparous reproduction, meaning that they flower (reproduce) only once and then die, and take years (up to 20 years for some species) to reach flowering age) or will be flowering later this summer (it’s too cool in the mountains right now and too early for them to flower yet at this altitude (2300 m)). However, we did find one flowering near the house where we were staying, so I set up shop there.

The goal of my infrared monitoring is to model bat visitation to agaves (aka feeding) as a function of numerous variables, including the density of flowering agaves in a site, the number of umbels (or groups of flowers) on the agave that have open flowers, etc. If I can figure out what attracts these bats to certain agaves over others, then we can start working with communities in the area to implement agave management strategies that cater to the bats’ needs. At least that’s the idea! I will be doing this by counting the visits of bats to the open flowers on two focal agaves per night within a site, one within the “worst” patch (i.e. the spot within the site with the lowest density of flowering agaves) and one within the “best” patch (i.e. the spot within the site with the highest density of flowering agaves), and measuring a host of variables of the focal agave and the agaves in the immediate area around the focal one.

For anyone who is potentially interested, the equipment I’m using is:

Two Sony FDR-AX33 camcorders with NightShot: $799 each; Bought as a bundle from Beach Camera. Each bundle included one small tripod that I'm using to mount the IR lamps, one Sony brand NP-FV70 rechargeable battery (which as I'll talk about below was a "good" battery that lasted about 2 hours), two off-brand batteries for the camcorder (beware of these, they suck and only lasted about 20-30 minutes!), a carrying case, and some other smaller accessories.
Two infrared lighting systems from Bat Conservation and Management: Each full system is $679 and includes two infrared lamps, one 12V 5 mAh battery (that powers the two IR lamps for about 4 hours), a carrying case for the system, and all the charging components
Two bigger/sturdier Ravelli APGL4 Professional 70" tripods for mounting the camcorders: $65 each, bought from Amazon
A pair of Bushnell 2x40 Equinox Z Digital Night Vision binoculars: $339; Purchased from B&H Photo, a company that I've really enjoyed working with

From personal experience I know how helpful it can be to read about what others have done/used in the field, so I hope this info may be useful for someone in the future! If you have more questions about all this you can email me directly at klear@uga.edu (or kristen.lear@gmail.com).

For this first night of monitoring I only did a “test run” using one camera setup instead of both, so I could test how long the camcorder and IR lamp batteries lasted and so that I could monitor the agave for a longer period of time to determine what time during the night the bats are most actively foraging (so I can target this timeframe in future monitoring nights). Unfortunately, I didn’t see any bats (likely because they aren’t in the area yet given that there are so few flowering agaves right now) but I’m kind of glad because I made an unfortunate discovery that the “off-brand” camcorder batteries are terrible! They only lasted between 20-40 minutes (versus the over 2 hours for the Sony brand battery). I thought it was because of how cold it got that night (45°F) but unfortunately when I tested them the next day in the office in normal temperatures they only did nominally better.

And the worst part was that the batteries weren’t just dying quickly, they were also dying without ANY warning. In fact, the battery indicator said over an hour was left each time when the battery died suddenly. AND when the camcorder died suddenly, the video recording wasn’t properly saved, so each time that happened I lost all the “data”. This is going to be problematic for when I actually see bats, so I’m going to have to take a precautionary approach when using the crappy batteries by stopping and restarting the recordings every 10 minutes or so, and only using each crappy battery for about 20 minutes to minimize the risk of them dying unexpectedly. Not ideal, but it’ll have to be good for now since buying more right now isn’t really an option…

Setting up the Sony camcorders and infrared lights to monitor the focal

agave for bat feeding at the flowers. (photo courtesy of Isra Castrejón)

After monitoring from 10:00pm to 2:30am, I hit the hay for a few hours before getting up at 8:00am to do the agave survey around the focal agave. We measured things like the height of the focal agave flowering stalk, the number and phenological state (e.g. without stalk, with flowering stalk, dead, etc.) of all the other agaves within a 15m radius circle of the focal agave, and took photos to be used in identifying the species later.

We started our drive home after the survey, and got back to Monterrey in the evening. We’ll be going to another site next week (Ejido Estanque de Norias and Rosillo Cave (a suspected maternity cave for the Mexican long-nosed bat where females give birth to and raise their pups)), where I’ll be doing another community leader interview and another night of bat monitoring. I am definitely glad I tried all the equipment out this week and I hope next week’s expedition goes well, with lots of bat activity. Check back later to find out how it goes!