diff --git a/adoption_sources/rescue_groups.py b/adoption_sources/rescue_groups.py
index 883a64f..2313613 100644
--- a/adoption_sources/rescue_groups.py
+++ b/adoption_sources/rescue_groups.py
@@ -62,13 +62,17 @@ def _build_species_filters(species: Sequence[str]) -> tuple[list[dict], str]:
     documented RescueGroups multi-species search example. #124 was silently
     rejected by the live API (zero results), so any change here must be
     re-verified against the real API (tests/test_rescue_groups_live.py).
+
+    The API's documented operations are ``equal``/``notequal``/``contains``/
+    etc. -- there is no ``equals``, and an unrecognized operation is silently
+    ignored, which is why #124 returned zero results.
     """
     if not species:
         raise ValueError("At least one species is required")
     filters = [
         {
             "fieldName": "species.singular",
-            "operation": "equals",
+            "operation": "equal",
             "criteria": FILTER_SPECIES_SINGULAR[plural],
         }
         for plural in species
diff --git a/cutepets.log b/cutepets.log
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_rescue_groups.py b/tests/test_rescue_groups.py
index 4642dbe..36a5e24 100644
--- a/tests/test_rescue_groups.py
+++ b/tests/test_rescue_groups.py
@@ -49,8 +49,8 @@ def test_two_species_uses_or_filter_processing(self):
         self.assertEqual(
             filters,
             [
-                {"fieldName": "species.singular", "operation": "equals", "criteria": "Dog"},
-                {"fieldName": "species.singular", "operation": "equals", "criteria": "Cat"},
+                {"fieldName": "species.singular", "operation": "equal", "criteria": "Dog"},
+                {"fieldName": "species.singular", "operation": "equal", "criteria": "Cat"},
             ],
         )
         self.assertEqual(filter_processing, "1 OR 2")
@@ -174,8 +174,8 @@ def test_posts_single_multi_species_request(self, mock_session_factory):
         self.assertEqual(
             payload["data"]["filters"],
             [
-                {"fieldName": "species.singular", "operation": "equals", "criteria": "Dog"},
-                {"fieldName": "species.singular", "operation": "equals", "criteria": "Cat"},
+                {"fieldName": "species.singular", "operation": "equal", "criteria": "Dog"},
+                {"fieldName": "species.singular", "operation": "equal", "criteria": "Cat"},
             ],
         )
         self.assertEqual(payload["data"]["filterProcessing"], "1 OR 2")