In these consolidated pro se appeals, Richard Max Strahan challenges the summary dismissal of separate lawsuits alleging violation of § 9 of the Endangered Species Act (“ESA”), 16 U.S.C. § 1538(a). The lawsuits were brought on behalf of listed species of whales, and in one case, also on behalf of listed species of sea turtles. For the following reasons, we affirm.

Strahan v. New England Aquarium challenges the practices of whale watch vessels operated by the New England Aquarium and the Dolphin Fleet of Provincetown, Inc. Strahan v. Hurst challenges United States Coast Guard operations. In both cases, defendants filed motions for summary judgment and Strahan sought extensions of time for responding. Roughly three months after the last extension expired, and in the absence of any further filings by Strahan (must less any document supporting an opposition to defendants’ motions), the district court dismissed the two suits for lack of prosecution under Fed.R.Civ.P. 41(b) and on the alternative ground that the motions for summary judgment were well-founded.

A summary judgment motion cannot be granted based on an adverse party’s failure to respond. See Carmona v. Toledo, 215 F.3d 124 n. 9 (1st Cir. 2000); Fed. R.Civ.P. 56(e) (if adverse party fails to respond, “summary judgment, if appropriate, shall be entered”) (emphasis added). However, there is some authority that, notwithstanding this rule, a case can be dismissed at the summary judgment stage under Rule 41(b) if the court determines that the plaintiff’s failure to respond constitutes a failure to prosecute. See, e.g., Custer v. Pan American Life Ins. Co., 12 F.3d 410, 415 (4th Cir. 1993); Lediju v. New York City Dep’t of Sanitation, 173 F.R.D. 105, 110 (S.D.N.Y. 1997).

In the instant case, Strahan’s failure to meet the extended deadlines for filing oppositions fell against a recent background of missed deadlines and delay on his part. Contrary to his suggestion, a warning is not an absolute requirement before dismissal. See Robson v. Hallenbeck, 81 F.3d 1, 3—4 (1st Cir. 1996). Strahan had the opportunity to explain his defaults by way of a motion to reinstate. He filed such a motion but did not proffer any valid excuses.

Arguably, Strahan’s conduct rose to the level of a failure to prosecute under Rule 41(b). However, we need not decide whether the dismissals can be upheld on this basis alone. The district court did not purport to dismiss the two cases solely on this ground but rather made an independent determination that summary judgment was warranted. Upon review of the record, we, too, are persuaded that the dismissals were otherwise justified.

Summary judgment was warranted in New England Aquarium based on Strahan’s failure to comply with Loc. R. 56.1, which justified the court in deeming admitted the facts presented in the movants’ statements of undisputed facts. See Ruiz Rivera v. Riley, 209 F.3d 24, 28 (1st Cir. 2000). Strahan suggests on appeal, without record citation, that the record contains “several scientific studies” sufficient to create a material issue of fact. However, the presence of Loe. R. 56.1, requiring Strahan to file a response to guide the court, removed any requirement that otherwise might exist that the district court ferret through the record before ruling on *10 defendants’ summary judgment motions. See Jaroma v. Massey, 873 F.2d 17, 21 (1st Cir. 1989). In any event, Strahan fails to specifically identify any of these studies or explain how they enhance his claims. 1

The dismissal in Hurst was warranted based on Strahan’s failure to comply with the sixty-day notice requirement before filing suit. See 16 U.S.C. § 1540(g)(2)(A)(i) (providing that a citizen may not bring suit under the ESA prior to sixty days after written notice of an alleged violation has been given to the Secretary and the alleged violator). Strahan sent his notice of intent to sue on March 19, 1998, and the complaint was filed only twenty-eight days later. This court has interpreted the sixty-day notice requirement in environmental statute citizen suits strictly. See Water Keeper Alliance v. United States Dep’t of Defense, 271 F.3d 21, 29 (1st Cir. 2001). 2

Affirmed.