Monday, October 30, 2017

Creepy Tarantulas and Tarantula Hawks













This week’s blog is about one of Sunol’s creepy crawlers—the tarantula. It lurks in the dark and doesn’t come out until October. It’s furry and looks menacing, but is it?

In Sunol there are two types of tarantulas: the blond and the brown tarantula. Pictured below is a brown tarantula or Aphonopelma smithi. This fellow was spotted by our field engineer, Ryan Dougherty.




If you’ve noticed an increase in spotting them, you’re not alone. In fact, it’s mating season for these giant arachnids. Male tarantulas will spend a lot of time weaving webs just above ground, outside the female’s burrow. If you don’t have a keen and trained eye, it is very difficult to tell the difference between a male and female tarantula. A typical tarantula reaches maturity at around 10 years. Most males die within a year after mating and females can live up to 25 years.

If provoked, the tarantula may inflict a painful bite, about like a bee sting. However, tarantulas tend to have a gentle nature, and rarely uses it’s fangs except to catch prey. If proved, it may raise its front legs and its abdomen to look aggressive. It may also release stinging hairs from its abdomen. These hairs irritate the skin of an attacker by digging themselves in with hundreds of tiny hooks.

They eat a variety of insects and other invertebrates, and their diet sometimes includes lizards, snakes and small rodents. They bite their prey, injecting it with digestive juices. Then they mash it with their strong jaws, and drink the liquid.

The tarantula’s feeding habits are gruesome but it's predator, the tarantula hawk, takes the word “gruesome” to another level. The tarantula hawk is a huge spider wasp. When the female tarantula hawk is ready to lay her eggs, she leaves the flowers behind and goes on the hunt for a tarantula. Once she finds one, she paralyzes it with a sting. Even though the tarantula is several times her own weight, she drags it to a hole, lays her eggs on it, and buries it. The eggs soon hatch into wasp larvae which slowly devour the paralyzed tarantula alive, from the inside out. Below is a picture of a tarantula hawk. Don’t let their beauty deceive you.



Image courtesy of San Antonio Express-News

If you are hiking in or around Sunol be on the lookout for these furry arachnids. Though they have fangs and carry poison, tarantulas are not considered a serious threat to humans. Please try not to step or run over one.

Happy Halloween!

Thursday, October 5, 2017

New Fish Screens at Fish Passage

Last week several members of our Fish Passage project took a trip to Sacramento to examine the project’s fish screens designed by Intake Screen Inc. (ISI). Next week, our team will be installing four of these fish screens at Fish Passage Facilities located in Alameda Creek.

Pictured below is one of the four new fish screens.



Here is Yen Ng, one of our project engineer’s; looking through what is called an internal cylinder brush. The internal cylinder brush is a key component of the fish screen.



Below is a diagram of a fish screen and its significant components.


Image courtesy of http://intakescreensinc.com/

The goal of the Fish Passage Project is to provide for safe passage of fish around the Alameda Creek Diversion Dam to support the restoration of Steelhead trout to the Alameda Creek Watershed. The project is part of the San Francisco Public Utilities Commission’s $4.8 billion Water System Improvement Project (WSIP) to repair, and seismically upgrade portion of the Hetch Hetchy Regional Water System.

Construction is expected to be completed in fall 2018.

See you around the valley!