The data doesn't necessarily indicate that the traders are betting on price declines.
FTX's U.S. affiliate has limited offerings, compared with its international counterpart.
Blockchain data firm Kaiko analyzed trading activity on centralized exchanges from different days and time zones.
"There was a flurry of call buying and put selling after the London fork," one trading firm said.
Put-call open interest ratio measures the number of open positions in put options relative to calls.
U.S.-based traders are able to use virtual private networks designed to mask the country where they are based. Or they simply lie about where they are from.
Users in some European countries will be unable to open new derivative positions, effective immediately.
"We didn't want to make this a thingy," Binance CEO Changpeng Zhao posted Monday on Twitter, a week after making the change.
Options traders are pricing an 8% chance of the cryptocurrency rising to a new peak above $64,800 by Dec. 31.
A combination of falling price and rising open interest is said to signal bearish conviction on the part of bitcoin futures traders.
Some 21,000 unique participants took part in the offering.
A strangle is essentially a bet that bitcoin’s price won’t break out anytime soon.
The last time the put-call ratio dropped to six-month lows was during the December-January bull run.