Flowers for Bats campaign

Greetings! This year's Flowers for Bats campaign has come to a close. Thank you for your efforts tracking flowering of cacti and agave! Read on to find out what we learned from your observations this year. Your data are making important contributions to help the USFWS understand when and where nectar sources are available for the lesser long-nosed bat, and how these nectar sources respond to changes in the environment. We hope that you will join us again next year. Your observations made at the same sites over multiple years are especially valuable in helping us to understand the variation in flowering in cacti and agave.

Closed flower buds on Agave palemeri

What you reported on saguaro and agave this year

This year, 140 observers reported data at 102 sites, up from 94 sites last year - thank you! The map below show sites reporting on the seven Flowers for Bats species. The color of the marker represents the species; larger markers represent more records reported at that site.

We had 19 partners report data on cacti and agave this year (up from 15 last year), along with 59 backyard observers. We appreciate our partners because they provide training for volunteers, bring in data from hard to reach locations, and participate in a variety of other conservation efforts related to the lesser long-nosed bat. Our backyard observers provide critical information about flowering timing across the urban to rural gradient.

In 2021, you captured a total of 149 onsets of open flowers for all species - 102 for saguaro, 34 for Agave palmeri, 7 for Agave deserti, 2 for Agave americana, 2 for Agave parryi, and 1 for organ pipe cactus. The two most commonly observed species, saguaro and Agave palmeri, provide nectar for bats at different times of the year. Now that we have multiple years of data, we can start to look at timing of nectar availability in these species. In the past four years, saguaro flowers opened in early April, peaked in May, and ended in mid-July. In 2021, the average onset date for open flowers in saguaro was May 18th, and the average duration of open flowers was 19 days. The average date on which saguaros had at least 75% of flowers open was May 27th. During these years observers also recorded additional flowering through November. This year was unique in that observers reported a small proportion of open flowers in the first four months of the year; this was not reported in the prior three years.

Agave palmeri open flowers varied more between years than did saguaro. This year had a similar peak in open flowers as 2019 and a similar end in open flowers to 2020. In 2021, the average onset date for open flowers in Agave palmeri was July 5th, and the average duration of open flowers was 51 days. The average date on which Agave palmeri had at least 75% of flowers open was August 30th.

As we continue to add to this dataset, we'll continue to discover patterns of when agave and saguaro have flowers, when the peak occurs, and explore how climate variables such as temperature and precipitation influence flowering phenology.  We hope that you will join us again next year to continue reporting on your saguaros and agaves. You are helping us to learn more about when and where flowers are available for bats and other pollinators!

Would you like a Flowers for Bats sticker (pictured at right)? Send your mailing address to erin@usanpn.org and we will mail one to you. Thank you for your contributions to this important project, we couldn't do it without your efforts!

Contact Erin Posthumus erin@usanpn.org 520-621-1670 bio

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