My colleagues have already addressed the types of intellectual property law protections available to you on the federal and state level. But there is another key point---obtaining a copyright or trademark is just the first step--and the easiest step--in protecting your rights. The hard part---and the most important part--is to exercise diligence in enforcing your IP rights against infringers. Just because you have invested in copyright and trademark protection does not prevent one of your competitors from stealing your intellectual property so as to lure away or confuse your customers. IP rights are worth nothing unless you are prepared to take aggressive steps to enforce them. This means working with legal counsel to prepare and send cease and desist letters, negotiate licensing arrangements and/or prosecuting infringement litigation. Many small business owners make the mistake of believing that if they pay the fees required for copyright and trademark infringement, they are done investing the amounts required for strong IP protection. Nothing could be further from the truth. IP protection requires vigilence---and that means retaining experienced IP litigation counsel to work closely with your company to enforce y our IP rights. Absent an IP enforcement strategy, the IP that you procure may not be worth the paper it is printed on.
If the mascot is part of your registered logo, it is already protected to the extent that someone else using the mascot would cause confusion with your logo. To get the strongest protection for the mascot, you could register a trademark for the mascot alone. Similarly, the mascot is protected against literal copying to some extent by your existing copyright in your logo, particularly if it is registered with the Copyright Office. But for the strongest protection, again you could register the mascot alone as a copyrighted work.
I am assuming when you say "mascot", you mean a graphic representation of a person or character, and not a sports mascot where a person is literally dressed up in a costume. There is no copyright protection for costumes, but I suppose a costumed mascot could still be protected as a trademark in theory, although in practice it might be difficult to register.
Unlike my colleague I thought "mascot" did mean a person dressed as a character. If the logo is a ladybug, then the mascot would be a person dressed as a ladybug used in promotion and merchandising. If you have the copyright and the trademark, then together with laws on unfair competition you should be pretty well protected.
The above is general legal and business analysis. It is not "legal advise" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
I agree with my colleagues' answers and would just add the following to their answers.
I cannot think of any way to obtain trademark or service mark protection for a character in the form of a live mascot. However, my understanding of copyright protection for a character might extend to that use. For instance, performance rights can be copyrighted and a mascot's performance should qualify for that. Of course, copyright protection would also extend to any media in which the mascot is used, i.e. a cartoon, drawings, packaging, TV commercials, etc.
Trademark protection is available for a character only in the sense that the 2 or 3 dimensional fixed image (or perhaps a moving image) is consistently used in the same exact manner and display of that character with the advertising of the service or the packaging of the product. For example, Tony the Tiger can be a registered trademark for cereal but only in the specific positions and images that are displayed on the cereal boxes (or perhaps in point of sale displays). A cartoon with Tony the Tiger might be protectible if also able to be displayed with the sale and delivery of the cereal. But the trademark protection of Tony the Tiger extends only to the exact positions, displays, etc. actually used as a mark on the various goods it promotes when those goods are sold or the services performed and rendered. Kelloggs cannot claim that a single use of a standing Tony the Tiger covers the various sitting down, lying down and running Tony the Tigers. Of course, Kelloggs might also have registered all those variations of Tony the Tiger and claims them all as trademarks.
But as my colleagues have stated, "unfair competition" laws should fill in many of the gaps and allow you to pursue any business that blatantly knocks off or imitates the use of your character in order to sell their goods/services. That said, there may be First Amendment "fair use" exemptions from their liability for infringing your character mark or copyright or unfair competition claims, i.e. if they are using the character to convey a message of public interest and not to sell a product or service, etc.
If you want more detailed and specific advice, I would suggest that you find and retain an IP lawyer. This site should be helpful for your identification of such a lawyer.
Alex Butterman is a trademark attorney with Staas& Halsey LLP (http://www.staasandhalsey.com), a Washington, D.C. IP boutique law firm. Alex is admitted to the bars of Washington, D.C., New York and New Jersey but, unless otherwise specified, the answer is intended to be general enough to apply to any U.S. state and based primarily upon his knowledge and experience with applicable federal laws. The opinions expressed are those of the author and do not necessarily reflect the views of his firm, Avvo or other attorneys. This answer is for general information purposes only and is not intended to be and should not be taken as legal advice. No attoreny-client relationship or obligations are established herein, although consulting an attorney to discuss your specific situation is strongly recommended. This is especially true of trademark law and probably any area of intellectual property law because TM law is so fact-specific and full of esoteric nuances and exceptions, that more often than not there does seem to be harm in handling a trademark matter without consulting an experienced trademark attorney.