Sierran Chorus Frog Page 1 Pacific Tree Sierran Chorus Frog: Pseudacris sierra Tree frogs are a whole family of frogs that live in trees. The least arboreal member of the group is our Pacific Tree Frog. People often ask, did our Pacific Tree Frog get renamed to the Pacific Chorus Frog? Tree frog is in the genus Hyla; chorus frog is in the genus Pseudacris. For awhile our Pacific Tree Frog was determined to be more genetically similar to chorus frogs. So its genus was changed from Hyla to Pseudacris. Then it changed back. Now it’s back to Pseudacris. Not only is it a chorus frog … it’s no longer a Pacific chorus frog. The latest news is that the frog has been split into three species: Pseudacris hypochondriaca - Baja California Treefrog, Pseudacris regilla - Northern Pacific Treefrog, and Pseudacris sierra - Sierran Treefrog. Technically, our frog is the Sierran tree frog. The great thing is that the frog itself doesn’t know or care. Identifying characteristics: . Enlarged bulbous toes allow the frog to cling to vertical surfaces. (If you find a small red- legged frog – it won’t have toe bulbs or an eye stripe.) . Color polymorphism: There are three main color traits: o Yellow-green o Brown (beige-brown) o Ability to change between yellow- green and brown . All tree frogs can change their brightness in response to temperature, humidity, and stress due to a hormone that regulates how much melanin is expressed. Almost all of them can . Dark stripe through eye. (Even though there get almost black. Their ability to change color are many color variations, this is our only frog is not instantaneous – and it can be observed. with a dark stripe through its eye.) How do you tell males from females? Throat pouches of males expand to make sound. When you look at a tree frog, the males will have dark and wrinkly throats. male with dark throat (usually smaller than female) female with pale throat ACR Natural History Note developed by Gwen Heistand for use in ACR Education (Much of this material has been presented over the years by David Herlocker. All photographs by Gary Nafis, www.californiaherps.com unless otherwise noted) Sierran Chorus Frog Page 2 Vocalization Calling starts after first significant autumn rain and lasts through June. Only males sing! (“I wanna woman” “I need a date I need a date” “I’m a guy, I’m a guy”). There are three basic calls: . Diphasic (krick eck… krick eeck) is a male attractant. It’s a call to gather. The more males that gather and call, the more females can hear and they’ll know it’s a good place to come and lay eggs. So, females also move toward diphasic calls. Monophasic (reeck / reeck / reeck) signals that a male is on territory and senses movement. He’s saying “Occupied / Occupied / Occupied”) . Trill (like a monophasic call with a trill at the end) can mean 2 things: 1) Actual contact with another male (“You’re too close to my territory!”); 2) Release call (“Get OFF me – I’m a guy!”) In the frog chorus (diphasic calls), we almost always hear 3 voices at the beginning of the chorus: 1. chorus leader (highest pitch) krick eek 2. second (next highest) krick eek 3. third (lowest in pitch) krick eek Then everybody comes in (at first in other triads and then it becomes that loud cacophony you hear driving past ponds at night.) The chorus leader is larger, has a stronger voice, and is in the best spot. If you go to a place where frogs are chorusing and CLAP, the chorus will stop. You can hear the chorus leader and his triad start up, then other triads, then the cacophony. They’ll start up again after about 5 minutes. (The Pacific Tree Frog is the frog heard round the world. Hollywood goes out into the back lot and records frogs. Rent the movie the African Queen and listen.) Reproduction Mating happens at night. Courtship happens in the day. At BLP we can hear tree frogs both day and night. How do frogs mate? . Frogs don’t have penises. Eggs are fertilized externally . The male rides on the back of the female (called amplexus) and kind of squeezes the eggs out of her. She lays eggs in masses almost as large as her, producing a protein that binds the egg mass together (kind of like jell-o). He releases the sperm over the eggs. The female can produce 2 or 3 egg masses per night and do this 2 or 3 nights per week amplexus ACR Natural History Note developed by Gwen Heistand for use in ACR Education (Much of this material has been presented over the years by David Herlocker. All photographs by Gary Nafis, www.californiaherps.com unless otherwise noted) Sierran Chorus Frog Page 3 Eggs are amazing, living, breathing things. They are metabolizing and producing wastes. Tree frog eggs start out in a clear, gelatinous, matrix. This matrix turns an amber-green color as the egg mass ages. The color is caused by algae actually growing within the “jell-o”. Algae keep oxygen levels high enough for the eggs. The gel acts as a greenhouse, allowing light to penetrate and keep the eggs warmer. The dark color of the eggs aids in heat absorption. Life is just so amazing!!!! (Tree frog egg masses droop, California newt egg masses don’t – they’re rubbier.) Larval tree frogs (tadpoles) are vegetarians. A tadpole is a vegetarian food processing unit. If you look at a tadpole upside down, you can see its very large, coiled, vegetarian digestive tract. Algae are a super abundant food source. Tree frogs produce tons of young. The female frog only has to provide nourishment for a little while. When tadpoles first hatch, they don’t have mouthparts. They lay around for a week or so developing their mouthparts and living off the ends of their egg nutrition. When tadpoles start developing their legs, they are as large (mass-wise) as they are ever going to be. The month of May is a usually a great time at Parson’s Pond to observe tadpoles in all phases of development. Metamorphosis! When you find an adult frog …or even a frog that has legs and still has a tail … spend a little time marveling. There is not a single vegetarian adult frog. So our modest little tree frog tadpole has to change from being an aquatic vegetarian to a terrestrial carnivore. While this is happening frogs can’t process food. That’s what the tail is for! All the muscles in the tail are slowly resorbed and used as food. I know you all know this … and I can’t help but sit in amazement every time I remind myself of what is going on. Adulthood Pacific Tree Frogs can become sexually mature and return to the mating ponds in less than a year. MOST reproductively active tree frogs are 2 or 3 year olds. One of the questions that kids always ask is how long can they live? We don’t know ... as long as they stay cool and healthy – many years. ACR Natural History Note developed by Gwen Heistand for use in ACR Education (Much of this material has been presented over the years by David Herlocker. All photographs by Gary Nafis, www.californiaherps.com unless otherwise noted) Sierran Chorus Frog Page 4 When they migrate away from the water, they find a crevice or burrow. They feed year- round (at night). Most of what they eat are invertebrates … mites, spiders, insects. The distance between their eyes is typically the size of the largest prey they can eat. Like most frogs, prey is located by vision and they require movement to catch prey. The frog lunges with a large sticky tongue to catch the prey and bring it into the mouth to eat. One cool thing .. Frogs don’t have ribs, which is an adaptation for a hopping life style. Lungs inflate their bodies – like bouncing balls. When disturbed, they will typically hop a large distance or jump into the water and swim into vegetation to hide. At times they will use their cryptic body color to avoid predation by remaining motionless. ACR Natural History Note developed by Gwen Heistand for use in ACR Education (Much of this material has been presented over the years by David Herlocker. All photographs by Gary Nafis, www.californiaherps.com unless otherwise noted) .