Question of the Day: Why did the tarantula cross the road?

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If you’ve been to the Wilderness Park recently, you may have spotted tarantulas out on the fire trails, and you might well wonder:

Why are so many tarantulas out now?
Why are they crossing the roads?

The tarantulas you see out on the roads this time of year are all adult males, and they are out looking for females. They really have only one thing on their little tarantula minds, and they are pretty oblivious to anything else.

A male California Ebony Tarantula (Aphonopelma eutylenum) crossing Johnson’s Pasture Rd in the Wilderness Park. On the front legs you can see the tibial hooks or spurs that are used to grasp the female during mating. ©Nancy Hamlett.


The females are found in burrows that are scattered across the landscape, and the males search for them by alternating between walking in straight lines and walking in concentric circles until a female’s scent is detected, suggesting that a burrow is nearby. The males may travel as much as 3/4 of a mile looking for a mate, and if a road is in their path, they just trundle on across it.

Once a male has found a female’s burrow, he signals his presence by doing some fancy drumming on the ground at the burrow’s entrance. If the female likes his drumming, she will emerge from her burrow, and mating can commence. The male uses special hooks on its front legs (which you can see in photo above) to immobilize the female’s fangs and position her during mating.

Autumn is the mating season for tarantulas, so that’s when you’ll most likely spot the males out on their mating missions. If we look at the distribution of tarantula sightings reported on our iNaturalist project, you can see that over 80% of the observations were made in August – November.

Tarantula observations in the Wilderness Park by month. Nineteen of 23 iNaturalist observations (83%) were made in August – November.

It’s not clear exactly how many tarantula species reside in the Wilderness Park. Only one species – California Ebony Tarantula (Aphonopelma eutylenum) – has iNaturalist observations labeled as “Research Grade”, meaning that the identification has been confirmed by a consensus of other identifiers. Steindacher’s Ebony Tarantula (Aphonopelma steindachneri) has also been reported, but the identifications have not been confirmed.

Different Aphonopelma species look very similar and can be extremely difficult to distinguish without molecular data (see Hamilton et al., 2016), so we may never know whether one or two species are present in the Park. You can see all the reported iNaturalist observations of tarantulas in the Park here.

If you’d like to find out more about the tarantula’s life cycle, check out Ralph Washington, Jr.’s article in Bay Nature magazine.

California Biodiversity “Day” in the Wilderness Park

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Thanks to everyone who participated in California Biodiversity Day at the Wilderness Park on September 11, and thanks to the Park Rangers, who set up their canopy for us! During the official California Biodiversity Days, Sept. 4 – 12, seventeen new observations were reported to our iNaturalist project, including 14 taxa, of which 11 were identified to species.

Here are a few that were observed:

Telegraph Weed (Heterotheca grandiflora)

Telegraph Weed growing up Johnson’s Pasture Road on the “loop”. © Peri Lee · some rights reserved
Telegraph Weed – flower detail. © Peri Lee · some rights reserved

Telegraph Weed was the species most commonly reported in the Park during California Biodiversity Days. Its bright yellow flowers on tall stems (sometimes more than 5 ft) are a common sight in the Park in late summer and fall. It is a pioneer native species, growing along roadsides and in other disturbed sites.

The origin of the common name is hazy. Some think it’s because the tall, slim stalks stick up like telegraph poles. Others have suggested it’s because it readily colonized the areas disturbed by telegraph pole installation.

Threadleaf Groundsel (Senecio flaccidus)

Threadleaf Groundsel next to Palmer-Evey Mountainway. © travisbbotany · some rights reserved

Another late summer and fall bloomer, Threadleaf Groundsel’s bright yellow daisy-like flowers rise about the mass of pale gray-green threadlike leaves that give the shrub its common name. Many different bees like to visit Threadleaf Groundsel.

Small Carpenter Bee (Ceratina sp.)

A Small Carpenter Bee on California Aster (Corethrogyne filaginifolia) next to the Cobal Canyon Trail.
© Nancy Hamlett · some rights reserved

Small Carpenter Bees are related to the large carpenter bees you may have seen around your house, but they are much too small to be able to bore into wood to make their nests; instead they make their nests in the pithy stems of plants.

Woodland Skipper (Ochlodes sylvanoides)

A Woodland Skipper nectaring on Cliff Aster (Malacothrix saxatilis) next to the Cobal Canyon Trail.
© Nancy Hamlett · some rights reserved

Woodland Skippers are common in chaparral in the late summer and fall. The larval host plants are grasses, but the adults nectar on a wide variety of plants.

You can see all of the Biodiversity Day observations here.

Celebrate California Biodiversity Day in the Park September 11

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September 7, 2021 marks the third official celebration of California Biodiversity Day, an annual event created in 2018 to celebrate the state’s exceptional biodiversity and encourage actions to protect it.  This year organizations throughout the state are hosting California Biodiversity Day events from September 4 to September 12, 2021, and the City of Claremont Park Rangers together with the Friends of the Wilderness Park be celebrating in the Claremont Hills Wilderness Park on the morning of Saturday, September 11.

Join us on Saturday morning, September 11th and learn how to use your phone to record observations of Wilderness Park flora and fauna with iNaturalist!  Just look for the canopy near the North Mills entrance for more information! All iNaturalist observations made in California from September 4 – September 12 will automatically be added to the California Biodiversity Day 2021 iNaturalist project.

Already an iNaturalist user?

Please come and help show others to use the iNaturalist app! Contact Vicki Salazar, our Volunteer Coordinator, at vickisalazar01@gmail.com, to let her know when you will be able to come. (Please note that all Friends of the Wilderness Park volunteers are required to be fully vaccinated for COVID-19.)

New to iNaturalist?

iNaturalist is an online social network of people sharing biodiversity information to help each other learn about nature. iNaturalist is a collaboration between National Geographic and the California Academy of Sciences.  Anyone can participate in iNaturalist!

Before arriving on Saturday please:

  1. Go to iNaturalist.org and create a free account. You should see “SIGN UP” featured prominently on the homepage.   Otherwise, there’s a “Sign Up” link in the top right corner.
  2. On your smart phone, go to the Apple Store or the Google Play store and download the iNaturalist app.

Once you’ve signed up, you can enter observations from either your phone or computer.  The iNaturalist site has a really good explanation here:

https://www.inaturalist.org/pages/getting+started
The page also has links to video tutorials.

In addition, we have two printer-friendly handouts created from the iNaturalist guide:

The Wilderness Park Biota Project:

iNat_project_header

In addition to the “California Biodiversity Day” project, any observations you make in the Wilderness Park (at any time) will be automatically added to the “Biota of the Claremont Hills Wilderness Park” project. This project was created by the Friends of the Wilderness Park specifically for documenting the plants and animals of the Wilderness Park.

If you’d like to check out the CHWP project and see what’s already been reported, just go to:
https://www.inaturalist.org/projects/biota-of-the-claremont-hills-wilderness-park

A few tips for best practices:

  • If feasible, crop your photos to feature the subject, especially if it’s not clear whether the subject is the bird or the tree, for example.
  • Include a little description. For one thing, you can use the description to say what’s the subject.  But you can also note any additional details, interesting behavior, type of habitat, odors, etc. that may not be obvious from the photo.
  • Give the most specific ID you can, even if it’s not to the species level. For instance, “insect”, “snake”, or even “plant” or “animal” is better than just having “unknown”.
  • Give a little info about yourself in your profile – it increases your credibility.

Northern Harrier Hunting in Johnson’s Pasture

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In the winter, you can often see Northern Harriers in the Wilderness Park. Unlike other hawks that hunt from on high, these unusual hawks fly very low over the ground, looking and listening for rodents. They have a disk-shaped face looks and functions much like an owl’s, with stiff facial feathers helping to direct sound to the ears, and they rely on hearing as well as vision to capture prey.

Last week one was hunting in Johnson’s Pasture and stayed in the same area for more than an hour, allowing your intrepid photographer to snap enough photos that some of them came our more or less in focus.

Here you can see how close they fly to the ground at times.

The Northern Harrier flying very low over the side of Johnson’s Pasture Road. ©Nancy Hamlett.

In the Wilderness Park, you can often look down on them and spot the distinctive white patch on the rump.

The Northern Harrier flying low showing its white rump patch while a cyclist rides by on Webb Canyon Road. ©Nancy Hamlett.

This Northern Harrier must have been a female, as the females are brown above (males are grayish) and pale with brown streaks below.

Another view of the Northern Harrier hunting showing the brown color above and the distinctive white rump patch. ©Nancy Hamlett.

If you see one of these in the Park, take a few minutes to watch it. They’re awesome! They’re not likely to be here too much longer for this year. Although some are sighted in LA County throughout the year, most of the Northern Harriers migrate to the very northern US and Canada for the summer.

For more information on Northern Harriers, check out All About Birds.

Spring has sprung!

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Even though it’s only February, it’s already spring in Southern California. Green leaves and shoots are popping up all over, and the earliest flowering plants are starting to bloom.

One of the first to flower is the White-flowering Currant (Ribes indecorum), which is making a show all over the Wilderness Park just now. This large deciduous shrub of chaparral and sage scrub has lobed, wrinkled bright green leaves that are slightly sticky and clusters of small white flowers in loose, dangling clusters, which are visited by bees, butterflies, and hummingbirds. The photo of the flowering plant above was taken last week in Johnson’s Pasture.

In late spring and summer, the White-flowering Currant has blue-purple berries, which are attractive to birds.

Berries of Ribes indecorum.
A bright green, wrinkled leaf of Ribes indecorum
The undersides of the leaves of Ribes indecorum have hairs that give them a whitish appearance.

Lots more plants will be flowering soon, so keep your eyes out! If you like looking at and photographing plants and animals in the Park, please think about posting to iNaturalist. Anything you post in the Park will be collected by our Biota of the Claremont Hills Wilderness Park project.

P.S. We have no idea why the specific name is indecorum. This plant’s decorum seems fine to us!