- Author: Robert J Keiffer
Sounding like a curse out of the Harry Potter movies, the word "stabilmentum" refers to a zigzag-shaped line of spider webbing that orb weaver spiders add to their webs. There are unconfirmed theories as to its function ... to attract insects, to help camouflage the nearby waiting spider, or to create a visual barrier so that birds do not fly through the web. The only thing we know for sure is that the stabilmentum superficially resembles writing, or letters of the English alphabet, and thus the common name of "writing spiders" is given to the orb spiders.
Here you see a female Black and Yellow Garden Spider (Argiope aurantia)... one of the most common orb spiders found in North and Central America. Common in milkweed patches and wetland areas on the UC-Hopland Research & Extension Center, these spiders tend to be local staying in one place throughout their lifetime. The web is a distinctive circular shape up to 2 feet in diameter, with the dense zigzag-shaped stabilmentum in the Center. The spider is usually found up-side-down near this centerpiece awaiting its prey to become ensnared in the web.
A nightly ritual occurs where the spider consumes the circular interior part of the web and then rebuilds it each morning with fresh new silk. The spider may be recycling the chemicals used in web-building, but this has not been proven. These spiders are not harmful to humans.
- Author: Robert J Keiffer
The Northern Red-legged Frog (Rana aurora aurora) used to be the dominant frog species in many North Coast wetland habitats. The same held true at UC-HREC where this species was collected during the 1950s from the permanent water-bodied "sag ponds" located in what we refer to as "Lake Biological Area Pasture". Females reach up to 4 inches in length, with the males being a bit smaller. However, the introduction and rapid expansion of the Bullfrog (Rana catesbeiana) throughout the west, along with the introduction of warm water fishes such as bass and bluegill, contributed to the extirpation of many of the native red-legged frog populations.
Here you see a bullfrog (left) and a red-legged frog (right), each soon after metamorphosis from the tadpole stage (photo is not from HREC), showing the dramatic size difference. The much larger bullfrogs eat almost anything they can wrap their sticky tongues around, including red-legged frogs.
Researchers at HREC have proposed plans and research projects to rid the "sag ponds" of the introduced fish, reduce the bullfrog population, and re-introduce the Northern Red-legged Frog, but thus far have been unsuccessful in obtaining the funding to do so.
- Author: Robert J Keiffer
The Mexican free-tailed bat ( or Brazilian free-tailed bat) (Tadarida brasiliensis) is one of the most widespread mammals in the Western Hemisphere. The UC Hopland Research & Extension Center is near the northernmost extent of their summer range (southern Oregon). This is the bat species that is famous for large colony roosting in such places as Carlsbad Caverns in New Mexico where millions of bats are observed by public visitors as they exit their cave roosts at dusk. Migratory in nature, the Mexican free-tailed bat only occurs here in North America during the summer months, and migrates to South America during the winter months, although the precise winter range is not well understood yet (they are NOT in the Amazon Rain Forest).
Usually roosting in caves, this species will sometimes roost in buildings (there is one barn at HREC where they traditionally roost). They hunt insects such as moths, mosquitoes, beetles, flies, true bugs, wasps, and flying ants by using echolocation and tend to forage at higher altitudes than other bat species. Preliminary high-frequency recordings near UC-HREC have shown that they forage over chaparral habitat at the 3000' elevation range.
The tail of this bat species extends beyond the uropatagium (skin flap that connects the hind legs) which places them into the "free-tailed bats" family group called Molossidae. Their echolocation calls are partially audible (within our hearing range) and sounds like rapid "clicks".
Future research is really needed in order to better understand how this bat species and other bat species utilize the Mendocino County vegetation types.
- Author: Shane Feirer
In the coming months we will be highlighting different spatial layers that we have at Hopland REC. The images that are posted to the blog should be interactive maps that the reader can manipulate. The attached map contains the boundary of the Hopland Research and Extension Center.
/small>- Author: Robert J Keiffer
The UC Hopland Research & Extension Center houses a fine herbarium collection that contains almost 700 vascular plant species that have been collected from the Center over the last 60 years. The majority of the collections were done by Mr. Harold Heady and Mr. Alfred Murphy during the 1950s and 1960s, with significant additions added by botanist Kerry Heise during the 1990s and 2000s. There a a few of those species that were collected initially that have not been relocated on the Center since, and may have been lost from the Center due to a variety of environmental manipulations over the decades. Or, perhaps they are just few-and-far-between and have just remained hidden from knowledgeable eyes.
One of those plant species is the showy Chaparral Lily (also called Redwood Lily) (Lilium rubescens) which was collected on HREC during the 1950s. It is a rare perennial of dry wooded and brushland ridges and slopes. The white trumpet flowers are extremely fragrant, and they gradually turn to pink as they age. This photo is from an area of north-facing slopes located a few miles away on federal Bureau of land Management lands - South Cow Mountain Recreation Area, which borders the UC-HREC property on the northeast side.