Tierra de Oro Laboratory

Physiology and Ecology in the Pinyon-Juniper Savanna

Tag: Baja California

  • Bahia de los Angeles 2026

    It was a successful year for science and wildlife.

    Peninsular landscape on the trip down. 6/17/26

    Once again, I joined Dr. Drew Talley and Dra. Dr Natalia Rodriguez Revelo for a summer survey of the islands in Bahia de los Angeles, Baja California.

    Natalia and Drew on Jorobado. 6/19/26

    The work on the islands went well, and we got data regarding beetle populations from twelve islands. It is also a highlight of my year to spend the time with my best friend and our wonderful colleague.

    Although work on the islands can be challenging, we are usually done by late morning, and there is time for other activities. This year, I thought it would be interesting to test the thermal resilience of some of the beetle species. The specific idea is that beetles that produce defensive chemicals (like Eleodes does) would be more sensitive to extreme conditions such as high temperature when compared with undefended beetles (such as Philolithus in Santa Fe or Cryptoglossa in Bahia). This has been assumed to be the case, but has not been tested rigorously.

    My idea was simple: collect beetles from two species, one defended and one undefended, and test their survival at temperatures ranging from benign to lethal. My prediction would be that the undefended beetles would survive at higher temperatures than those that invest energy and water in defensive scent glands.

    We decided it was better to collect the experimental beetles on the mainland. The project was added to the permit application along with the other, ongoing projects. However, the permit only allowed us to survey the beetles on the mainland, not collect or test them. Nonetheless, sampling would allow us to determine where it would be best to find enough beetles for experiments in the future.

    Bahia de los Angeles dump. 6/18/26

    For our first sampling location, we set traps at the local dump. We reasoned that we could avoid protected areas and private property by sampling at the dump.

    We set nine pitfall traps, baited with oatmeal along an arroyo. After checking back every afternoon for three days, we had caught six Cryptoglossa muricata. It was good to find beetles that would be appropriate for experiments, but we needed at least two species, and about 40 of each. We thought it best to look elsewhere.

    One can see why beetles in the Cryptoglossini are called “death feigning beetles.” This C. muricata is quite alive, but waiting for me to go away. 6/20/26

    We thought that the Glendale Community College field station might be a better location, so we asked Jared Ocampo, an old friend and the station manager, for permission to set traps around the station. He agreed, and even helped us set the traps.

    Arroyo on the southern approach to the Glendale Station. 6/24/26

    We set a total of 24 traps in three sets of eight. One group was set in an arroyo to the south of the station, one set was placed in desert to the west, and the last was placed near the beach to the north. Rather than checking every day, we left the traps for two nights.

    The results were pleasing. We trapped more than sixty C. muricata, and ten Eleodes loretensis, along with a number of Stibia. This is an almost ideal result, in that E. loretensis is chemically defended, whereas C. muricata is not, and they are well-matched n terms of size and mass.

    Eleodes loretensis from a trap at Glendale station. 6/26/26. Click to enlarge.
    Cryptoglossa muricata from a trap in the arroyo at Glendale station. 6/26/26

    The traps in the arroyo were the most productive, and those in the desert also caught a good number of beetles. Interestingly, those by the beach only trapped a few Cryptoglossa.

    Assuming that all goes equally well next year and we have the proper permit, we should be able to compare the temperature sensitivities of these two species that are highly similar except for the presence of chemical defense.

    As always, there is more to come.

  • Baja California: Annual Island Survey

    The islands in the Gulf of California provide a natural laboratory for the effects of “spatial subsidy,” the movement of resources from a rich environment (the sea) to a more impoverished habitat (the desert islands). In this context, scientists have studied many species on the islands, including Tenebrionid beetles. The abundance and diversity of beetles on the islands of Bahia de los Angeles have been surveyed for at least 30 years, and my good friend and colleague Dr Drew Talley has been leading the studies for most of that time. In recent years, Dr Natalia Rodriguez Revelo, an expert in beetles and dune ecology, has participated in the work with Drew. I have participated in various roles for several of the past 20 field seasons, and was once again privileged to spend time with them and help out on the islands this year.

    Drew and Natalia counting beetles on La Ventana. 6/28/25.

    The procedure is straightforward in principle: on each island, set multiple pitfall traps (plastic party cups) baited with lean pieces of fish. The beetles (and, occasionally, other creatures) fall into the traps. Six days later, the traps are checked and the number and species of beetles are scored. In practice, mice or gulls can steal bait if it is not adequately secured, or fat from fish guts can turn the contents of the cup to smelly soup.

    In a perfect world, traps would be set on all of the accessible islands in the bay. In practice, time constraints forced us to prioritize. This year, we sampled Coronadito, Coronado (also known as Isla Smith), Flecha, Pata, Llave, Cerraja, La Ventana, Cabeza de Caballo, and Gemelos West.

    I made an effort this year to photograph each species using a platform with tacky wax to secure the beetle, and a scale to document its size.

    Satellite map of ahia de Lo
    Map of the bay at Bahia de los Angeles. Most islands, including all islands sampled this year, are labeled. The town of Bahia de los Angeles is labeled at lower left.

    It was marginally successful, and provided insight about how to improve future versions.

    Below is a draft guide to the beetles found on the islands, When possible, photos are provided of beetles held in fingers and mounted on the photography platform. Cartoons provide graphic representation of the relative sizes of the beetles, ranging from tiny (Batuliodes) to hefty (Cryptoglossa), keeping in mind that the sizes of all species can vary significantly.

    Distribution of each species are based on data from Sanchez Piñero and Aalbu (2002). A table extracted from their observations can be found here.

    Click the photographs if you want to see larger versions.

    Argoporis apicalis

    Medium sized, with ridged elytra and reddish legs. Argoporis is one of the few Tenebrionids on the islands which possess defensive glands in their abdomens.

    Found on all islands except Mitlan (tiny island next to Coronado).

    12 mm
    narrow black beetle with reddish legs held by fingers
    Argoporis apicalis trapped on Coronadito island. 6/26/25.
    Argoporis apicalis trapped on Cerraja island. The blurred image of an extra antenna was caused by using focus stacking to improve depth of field. 6/27/25.

    Batuliodes confluens

    This tiny brown beetle with roughened pronotum and elytra.

    Found on the majority of islands, and may be undercounted due to its small size.

    tiny black beetle on a white background
    ~3 mm
    Batuliodes confluens trapped on Flecha island. 6/23/14
    Batuliodes confluens trapped on Cerraja island. 6/27/25.

    Cryptadius tarsalis

    Small, oval, and deep-bodied, with dense rows of small punctures on the elytra.

    Cryptadius is found on Bota, Cerraja, Coronado, Jorobado, Mitlan and Pata.

    Diagram of a small beetle on a white background
    8 mm
    Cryptadius tarsalis.trapped on Llave island. Scale bar, 2 mm. 6/27/25

    Cryptoglossa spiculifera

    One of the largest beetles on the islands, with elytra decorated with rows of raised, spiny bumps.

    Found on the largest islands (Coronado, Cabeza de Caballo, but not La Ventana) as well as the rookery island, Gemelos West.

    diagram of a black beetle almost filling a white background.
    28 mm
    Cryptoglossa spiculifera trapped on Gemelos West island, 6/28/25.
    Large black beetle on blurred blue background.
    Cryptoglossa spiculifera trapped on Gemelos West island. Scale bar, 10 mm. 6/28/25.

    Microschatia championi

    Slightly smaller than Cryptoglossa, the elytra of Micoschatia are decorated with dimples rather than sharp bumps and there are punctures on the lateral pronotum of M. championi.

    Present on all but the smallest islands.

    20 mm
    Microschatia championi trapped on Cerraja island. 6/27/25.
    Microschatia championi trapped on Cerraja island. Scale bar, 5 mm. 6/27/25.

    Stibia sparsa

    Shaped like a typical Tenebrionid, with dense punctures on the pronotum and rows of punctures on the elytra.

    Stibia can be found on the largest islands (Cabeza de Caballo, Coronado, La Ventana) plus Gemelos West.

    diagram of a black beetle on a large white background
    11 mm
    small brownish black beetle held in fingers
    Stibia sparsa trapped on Gemelos West island. 6/28/25
    dorsal view of black beetle on blurred blue background
    Stibia sparsa trapped on Gemelos West island. Scale bar, 2 mm. 6/28/25.

    Tonibius sulcatus

    Very small and reddish, with relatively smooth pronotum and strongly ridged elytra.

    Described from most islands, except Coronaditio, Gemelos West, Jorobado and Llave.

    diagram of a very small black beetle on a white background
    6 mm
    Tonibius sulcatus found at Las Hamacas hotel. 7/10/24.

    Triphalopsis californicus

    Small, black, oval, and deep-bodied. Covered with fine hairs that are often coated in dust.

    Triphalopsis has been described from all islands except Gemelo West.

    Diagram of a small beetle on a white background
    8 mm
    Triphalopsis californicus trapped on Flecha island. 6/27/25.
    Triphalopsis californicus trapped on Cerraja island. Scale bar, 2 mm. 6/27/25.

    There are many other beetles, including various species of Histeridae and Dermestidae (not shown).

    Hister Beetle on Coronadito Island. Scale 2 mm. 6/26/25.

    Centipedes, spiders, and scorpions are often found in the traps in the larger islands.

    Scorpion trapped on La Ventana. 6/28/25

    References

    Sanchez Piñero, F. and Aalbu, R. L. (2002). Tenebrionid Beetles (Appendix 6.1). In A New Island Biogeography of the Sea of Cortés, pp. 129–153. New York: Oxford University Press.