Tobusch Fishhook Cactus

Ancistrocactus tobuschii

Description

Tobusch fishhook cactus,Ancistrocactus tobuschii, typically grows as a solitary top-shaped (turbinate) stem, up to 5 in (13 cm) tall and about
3.5 in (9 cm) thick. Each spine cluster (areole) consists of seven to nine radial spines and three light yellow central spines. The central spines have red (immature) or gray (mature) tips. One of the three central spines is distinctively hooked. Prominent yellow-green flowers bloom from mid-February to early April. Green fruits mature by the end of May and split open to disgorge about twenty black seeds.

The genus Ancistrocactus (derived from Latin for "fishhook") contains four species, three from the Rio Grande River region in southern Texas and Mexico, and one endemic to Mexico. The species has also been known as Echinocactus tobuschii and Mammillaria tobuschii.

Habitat

The Tobusch cactus is found on the Edwards Plateau of Texas, a region of canyons and arroyos scoured by numerous seasonal creeks and rivers. The soil is derived from limestone and the dominant vegetation is juniper, oak, sycamore, and associated grasses. Livestock have grazed much of the plateau for many years, denuding ground cover and triggering localized erosion.

The Tobusch cactus occurs in gravels and gravelly soils along stream banks subject to periodic flash floods. During spring and fall, storms develop over the mountains of Mexico and stall over the Edwards Plateau, producing heavy downpours and torrential runoff. Although particularly severe floods will destroy plants, the scouring action of moderate flooding appears to benefit the Tobusch cactus by removing competing plants and grasses. Habitat elevation is about 1,600 ft (490 m).

Distribution

The Tobusch fishhook cactus was once more abundant in a five-county range comprising northern Bandera, western Kerr, and most of Kimble, Real, and Uvalde counties. The population at the discovery site near Vanderpool (Bandera County) was eliminated when the ground was cleared in the 1960s.

At the time of federal listing in 1979, fewer than 200 plants were known to survive. Six populations were surveyed in 1985, adding to the population count, but a current estimate of total numbers does not exist.

Several populations grow along the Sabinal River in Bandera County. A small population on the river above Vanderpool, believed extirpated, was rediscovered in 1985. Kimble County populations are northeast of Segovia and near the town of Junction. In Uvalde County, a small population occurs north of the town of Uvalde. In Real County, north of Leakey on the Frio River, a population survives at a site formerly used for grazing. Here, a strong population of seedlings has taken root around mature plants.

Threats

The decline of the Tobusch fishhook cactus was initiated by overgrazing of the habitat by livestock. Animals trample or browse seedlings, preventing the establishment of new plants. Overgrazing contributes to erosion, which worsens flood damage. U.S. Fish and Wildlife Service (FWS) personnel have successfully negotiated with some private land owners to secure protected fields for the cactus.

While livestock continue to graze several sites, a more immediate threat to surviving plants is the loss of stream bank habitat to residential development. Stream and river front lots in the region are being promoted by real estate developers as sites for summer cottages.

Commercial collectors have also played a significant role in the decline of the species. Collectors return to the same sites year after year to dig up wild plants for sale. The damage they cause is intensified by the low number of surviving plants. The Endangered Species Act cannot protect plants from being collected on private land.

Conservation and Recovery

The primary goal of the FWS Recovery Plan is to establish four secure populations of 3,000 plants each. Reintroduction of the cactus to suitable sites within the historic range is anticipated. If recovery recommendations are actively pursued, this Endangered cactus could be considered for reclassification as Threatened very soon.

Contacts

U.S. Fish and Wildlife Service
Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103
http://southwest.fws.gov/

References

Marshall, W. T. 1952. "A New and Interesting Cactus from Texas."Saguaroland Bulletin 6(7):78-81.

U.S. Fish and Wildlife Service. 1987. "Tobusch Fishhook Cactus (Ancistrocactus tobuschii ) Recovery Plan." U.S. Fish and Wildlife Service, Albuquerque.

Weniger, D. 1970. Cacti of the Southwest. University of Texas Press, Austin.