Horseshoe SOS was developed by Naturedigger, LLC as an identification guide and introduction to one of our most unique and ancient marine animals.

Horseshoe SOS includes:

• Identification and geographic ranges of all four horseshoe crab species present in North America and Asia

• An Atlantic horseshoe crab Gallery filled with high res images of spawning crabs, eggs and juvenile crabs, as well as an ID section with annotated images of dorsal and ventral views, horseshoe crabs' unique eyes and much more...

• A Conservation section that lists organizations involved in horseshoe crab education and conservation. Browse their profile pages to see how their programs help horseshoe crabs and how they include the public in horseshoe crab conservation. (If an organization collects data using Horseshoe SOS, you will see a "New Report" tab in their profile. If a report tab is absent, the organization either doesn't collect data using citizen scientists or you must visit their website to input data)

• A Threats section spotlighting both natural and unnatural threats facing horseshoe crabs

• An awesome FAQ section that answers many pressing questions about horseshoe crabs such as: "Why are there so many dead horseshoe crabs on the beach?" and "Where and when are the best times to see horseshoe crabs spawn?" and "Why is a horseshoe crab's blood blue?" You will learn several ways the public can have a major, positive impact on horseshoe crab populations. We love to hear from you, so please use the Feedback email in the slide out menu of the app to submit your own questions for our FAQ section!

• A Research section for in-depth information about horseshoe crab conservation, population and management. You can access ERDG's searchable database in this section as well

• Reporting tagged horseshoe crabs to the US Fish and Wildlife Service (USFWS). Go to the Report Tag button on the main navigation menu and fill in the fields (especially the tag number) take a photo, then send your report, it's that easy! USFWS really appreciates these "resightings" and will send information about where and when the horseshoe crab was originally tagged and released

What’s New

Version 3.3

•Bug fixes

Ratings and Reviews

5.0 out of 5
3 Ratings

3 Ratings

Harold M ,

Excellent info on this ancient species

This app is top notch. It contains excellent information on horseshoe crabs, great pictures, some research and a list of organizations that are trying to help horseshoe crabs. The FAQ answers all if the most common questions people have about these wonderful creatures.

tony chest nut ,

Horseshoe Crabs

Great app.


Naturedigger LLC
37.1 MB

Requires iOS 13.0 or later. Compatible with iPhone, iPad, and iPod touch.



Age Rating


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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