diff --git a/gerbil-manager-web/package-lock.json b/gerbil-manager-web/package-lock.json
index f118bda..b6c48f6 100644
--- a/gerbil-manager-web/package-lock.json
+++ b/gerbil-manager-web/package-lock.json
@@ -9,6 +9,7 @@
       "version": "0.0.0",
       "dependencies": {
         "react": "^19.2.6",
+        "react-d3-tree": "^3.6.6",
         "react-dom": "^19.2.6",
         "react-router-dom": "^7.17.0"
       },
@@ -220,6 +221,15 @@
         "node": ">=6.0.0"
       }
     },
+    "node_modules/@babel/runtime": {
+      "version": "7.29.7",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.29.7.tgz",
+      "integrity": "sha512-Nq8OhGWiZIZGV6hLHoyAKLLcJihP/xFeBMGJoUrxTX2psI8dCifzLhZISFb+VWS3wFMRDmCGw5R+dOySCqPLhw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=6.9.0"
+      }
+    },
     "node_modules/@babel/template": {
       "version": "7.29.7",
       "resolved": "https://registry.npmjs.org/@babel/template/-/template-7.29.7.tgz",
@@ -268,6 +278,24 @@
         "node": ">=6.9.0"
       }
     },
+    "node_modules/@bkrem/react-transition-group": {
+      "version": "1.3.5",
+      "resolved": "https://registry.npmjs.org/@bkrem/react-transition-group/-/react-transition-group-1.3.5.tgz",
+      "integrity": "sha512-lbBYhC42sxAeFEopxzd9oWdkkV0zirO5E9WyeOBxOrpXsf7m30Aj8vnbayZxFOwD9pvUQ2Pheb1gO79s0Qap3Q==",
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "chain-function": "^1.0.0",
+        "dom-helpers": "^3.3.1",
+        "loose-envify": "^1.3.1",
+        "prop-types": "^15.5.6",
+        "react-lifecycles-compat": "^3.0.4",
+        "warning": "^3.0.0"
+      },
+      "peerDependencies": {
+        "react": "^15.0.0 || ^16.0.0 || ^17.0.0 || ^18.0.0 || ^19.0.0",
+        "react-dom": "^15.0.0 || ^16.0.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/@emnapi/core": {
       "version": "1.10.0",
       "resolved": "https://registry.npmjs.org/@emnapi/core/-/core-1.10.0.tgz",
@@ -868,6 +896,12 @@
         "assertion-error": "^2.0.1"
       }
     },
+    "node_modules/@types/d3-hierarchy": {
+      "version": "1.1.11",
+      "resolved": "https://registry.npmjs.org/@types/d3-hierarchy/-/d3-hierarchy-1.1.11.tgz",
+      "integrity": "sha512-lnQiU7jV+Gyk9oQYk0GGYccuexmQPTp08E0+4BidgFdiJivjEvf+esPSdZqCZ2C7UwTWejWpqetVaU8A+eX3FA==",
+      "license": "MIT"
+    },
     "node_modules/@types/deep-eql": {
       "version": "4.0.2",
       "resolved": "https://registry.npmjs.org/@types/deep-eql/-/deep-eql-4.0.2.tgz",
@@ -1459,6 +1493,21 @@
         "node": ">=18"
       }
     },
+    "node_modules/chain-function": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/chain-function/-/chain-function-1.0.1.tgz",
+      "integrity": "sha512-SxltgMwL9uCko5/ZCLiyG2B7R9fY4pDZUw7hJ4MhirdjBLosoDqkWABi3XMucddHdLiFJMb7PD2MZifZriuMTg==",
+      "license": "MIT"
+    },
+    "node_modules/clone": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/clone/-/clone-2.1.2.tgz",
+      "integrity": "sha512-3Pe/CF1Nn94hyhIYpjtiLhdCoEoz0DqQ+988E9gmeEdQZlojxnOb74wctFyuwWQHzqyf9X7C7MG8juUpqBJT8w==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.8"
+      }
+    },
     "node_modules/convert-source-map": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/convert-source-map/-/convert-source-map-2.0.0.tgz",
@@ -1501,6 +1550,132 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/d3-color": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/d3-color/-/d3-color-3.1.0.tgz",
+      "integrity": "sha512-zg/chbXyeBtMQ1LbD/WSoW2DpC3I0mpmPdW+ynRTj/x2DAWYrIY7qeZIHidozwV24m4iavr15lNwIwLxRmOxhA==",
+      "license": "ISC",
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/d3-dispatch": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/d3-dispatch/-/d3-dispatch-3.0.1.tgz",
+      "integrity": "sha512-rzUyPU/S7rwUflMyLc1ETDeBj0NRuHKKAcvukozwhshr6g6c5d8zh4c2gQjY2bZ0dXeGLWc1PF174P2tVvKhfg==",
+      "license": "ISC",
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/d3-drag": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/d3-drag/-/d3-drag-3.0.0.tgz",
+      "integrity": "sha512-pWbUJLdETVA8lQNJecMxoXfH6x+mO2UQo8rSmZ+QqxcbyA3hfeprFgIT//HW2nlHChWeIIMwS2Fq+gEARkhTkg==",
+      "license": "ISC",
+      "dependencies": {
+        "d3-dispatch": "1 - 3",
+        "d3-selection": "3"
+      },
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/d3-ease": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/d3-ease/-/d3-ease-3.0.1.tgz",
+      "integrity": "sha512-wR/XK3D3XcLIZwpbvQwQ5fK+8Ykds1ip7A2Txe0yxncXSdq1L9skcG7blcedkOX+ZcgxGAmLX1FrRGbADwzi0w==",
+      "license": "BSD-3-Clause",
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/d3-hierarchy": {
+      "version": "1.1.9",
+      "resolved": "https://registry.npmjs.org/d3-hierarchy/-/d3-hierarchy-1.1.9.tgz",
+      "integrity": "sha512-j8tPxlqh1srJHAtxfvOUwKNYJkQuBFdM1+JAUfq6xqH5eAqf93L7oG1NVqDa4CpFZNvnNKtCYEUC8KY9yEn9lQ==",
+      "license": "BSD-3-Clause"
+    },
+    "node_modules/d3-interpolate": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/d3-interpolate/-/d3-interpolate-3.0.1.tgz",
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+      "license": "ISC",
+      "dependencies": {
+        "d3-color": "1 - 3"
+      },
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/d3-path": {
+      "version": "1.0.9",
+      "resolved": "https://registry.npmjs.org/d3-path/-/d3-path-1.0.9.tgz",
+      "integrity": "sha512-VLaYcn81dtHVTjEHd8B+pbe9yHWpXKZUC87PzoFmsFrJqgFwDe/qxfp5MlfsfM1V5E/iVt0MmEbWQ7FVIXh/bg==",
+      "license": "BSD-3-Clause"
+    },
+    "node_modules/d3-selection": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/d3-selection/-/d3-selection-3.0.0.tgz",
+      "integrity": "sha512-fmTRWbNMmsmWq6xJV8D19U/gw/bwrHfNXxrIN+HfZgnzqTHp9jOmKMhsTUjXOJnZOdZY9Q28y4yebKzqDKlxlQ==",
+      "license": "ISC",
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/d3-shape": {
+      "version": "1.3.7",
+      "resolved": "https://registry.npmjs.org/d3-shape/-/d3-shape-1.3.7.tgz",
+      "integrity": "sha512-EUkvKjqPFUAZyOlhY5gzCxCeI0Aep04LwIRpsZ/mLFelJiUfnK56jo5JMDSE7yyP2kLSb6LtF+S5chMk7uqPqw==",
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "d3-path": "1"
+      }
+    },
+    "node_modules/d3-timer": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/d3-timer/-/d3-timer-3.0.1.tgz",
+      "integrity": "sha512-ndfJ/JxxMd3nw31uyKoY2naivF+r29V+Lc0svZxe1JvvIRmi8hUsrMvdOwgS1o6uBHmiz91geQ0ylPP0aj1VUA==",
+      "license": "ISC",
+      "engines": {
+        "node": ">=12"
+      }
+    },
+    "node_modules/d3-transition": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/d3-transition/-/d3-transition-3.0.1.tgz",
+      "integrity": "sha512-ApKvfjsSR6tg06xrL434C0WydLr7JewBB3V+/39RMHsaXTOG0zmt/OAXeng5M5LBm0ojmxJrpomQVZ1aPvBL4w==",
+      "license": "ISC",
+      "dependencies": {
+        "d3-color": "1 - 3",
+        "d3-dispatch": "1 - 3",
+        "d3-ease": "1 - 3",
+        "d3-interpolate": "1 - 3",
+        "d3-timer": "1 - 3"
+      },
+      "engines": {
+        "node": ">=12"
+      },
+      "peerDependencies": {
+        "d3-selection": "2 - 3"
+      }
+    },
+    "node_modules/d3-zoom": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/d3-zoom/-/d3-zoom-3.0.0.tgz",
+      "integrity": "sha512-b8AmV3kfQaqWAuacbPuNbL6vahnOJflOhexLzMMNLga62+/nh0JzvJ0aO/5a5MVgUFGS7Hu1P9P03o3fJkDCyw==",
+      "license": "ISC",
+      "dependencies": {
+        "d3-dispatch": "1 - 3",
+        "d3-drag": "2 - 3",
+        "d3-interpolate": "1 - 3",
+        "d3-selection": "2 - 3",
+        "d3-transition": "2 - 3"
+      },
+      "engines": {
+        "node": ">=12"
+      }
+    },
     "node_modules/debug": {
       "version": "4.4.3",
       "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.3.tgz",
@@ -1526,6 +1701,15 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/dequal": {
+      "version": "2.0.3",
+      "resolved": "https://registry.npmjs.org/dequal/-/dequal-2.0.3.tgz",
+      "integrity": "sha512-0je+qPKHEMohvfRTCEo3CrPG6cAzAYgmzKyxRiYSSDkS6eGJdyVJm7WaYA5ECaAD9wLB2T4EEeymA5aFVcYXCA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=6"
+      }
+    },
     "node_modules/detect-libc": {
       "version": "2.1.2",
       "resolved": "https://registry.npmjs.org/detect-libc/-/detect-libc-2.1.2.tgz",
@@ -1536,6 +1720,15 @@
         "node": ">=8"
       }
     },
+    "node_modules/dom-helpers": {
+      "version": "3.4.0",
+      "resolved": "https://registry.npmjs.org/dom-helpers/-/dom-helpers-3.4.0.tgz",
+      "integrity": "sha512-LnuPJ+dwqKDIyotW1VzmOZ5TONUN7CwkCR5hrgawTUbkBGYdeoNLZo6nNfGkCrjtE1nXXaj7iMMpDa8/d9WoIA==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.1.2"
+      }
+    },
     "node_modules/electron-to-chromium": {
       "version": "1.5.368",
       "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.5.368.tgz",
@@ -1987,7 +2180,6 @@
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/js-tokens/-/js-tokens-4.0.0.tgz",
       "integrity": "sha512-RdJUflcE3cUzKiMqQgsCu06FPu9UdIJO0beYbPhHN4k6apgJtifcoCtT9bcxOpYBtpD2kCM6Sbzg4CausW/PKQ==",
-      "dev": true,
       "license": "MIT"
     },
     "node_modules/jsesc": {
@@ -2338,6 +2530,18 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/loose-envify": {
+      "version": "1.4.0",
+      "resolved": "https://registry.npmjs.org/loose-envify/-/loose-envify-1.4.0.tgz",
+      "integrity": "sha512-lyuxPGr/Wfhrlem2CL/UcnUc1zcqKAImBDzukY7Y5F/yQiNdko6+fRLevlw1HgMySw7f611UIY408EtxRSoK3Q==",
+      "license": "MIT",
+      "dependencies": {
+        "js-tokens": "^3.0.0 || ^4.0.0"
+      },
+      "bin": {
+        "loose-envify": "cli.js"
+      }
+    },
     "node_modules/lru-cache": {
       "version": "5.1.1",
       "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-5.1.1.tgz",
@@ -2417,6 +2621,15 @@
         "node": ">=18"
       }
     },
+    "node_modules/object-assign": {
+      "version": "4.1.1",
+      "resolved": "https://registry.npmjs.org/object-assign/-/object-assign-4.1.1.tgz",
+      "integrity": "sha512-rJgTQnkUnH1sFw8yT6VSU3zD3sWmu6sZhIseY8VX+GRu3P6F7Fu+JNDoXfklElbLJSnc3FUQHVe4cU5hj+BcUg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/obug": {
       "version": "2.1.2",
       "resolved": "https://registry.npmjs.org/obug/-/obug-2.1.2.tgz",
@@ -2567,6 +2780,17 @@
         "node": ">= 0.8.0"
       }
     },
+    "node_modules/prop-types": {
+      "version": "15.8.1",
+      "resolved": "https://registry.npmjs.org/prop-types/-/prop-types-15.8.1.tgz",
+      "integrity": "sha512-oj87CgZICdulUohogVAR7AjlC0327U4el4L6eAvOqCeudMDVU0NThNaV+b9Df4dXgSP1gXMTnPdhfe/2qDH5cg==",
+      "license": "MIT",
+      "dependencies": {
+        "loose-envify": "^1.4.0",
+        "object-assign": "^4.1.1",
+        "react-is": "^16.13.1"
+      }
+    },
     "node_modules/punycode": {
       "version": "2.3.1",
       "resolved": "https://registry.npmjs.org/punycode/-/punycode-2.3.1.tgz",
@@ -2586,6 +2810,27 @@
         "node": ">=0.10.0"
       }
     },
+    "node_modules/react-d3-tree": {
+      "version": "3.6.6",
+      "resolved": "https://registry.npmjs.org/react-d3-tree/-/react-d3-tree-3.6.6.tgz",
+      "integrity": "sha512-E9ByUdeqvlxLlF9BSL7KWQH3ikYHtHO+g1rAPcVgj6mu92tjRUCan2AWxoD4eTSzzAATf8BZtf+CXGSoSd6ioQ==",
+      "license": "MIT",
+      "dependencies": {
+        "@bkrem/react-transition-group": "^1.3.5",
+        "@types/d3-hierarchy": "^1.1.8",
+        "clone": "^2.1.1",
+        "d3-hierarchy": "^1.1.9",
+        "d3-selection": "^3.0.0",
+        "d3-shape": "^1.3.7",
+        "d3-zoom": "^3.0.0",
+        "dequal": "^2.0.2",
+        "uuid": "^8.3.1"
+      },
+      "peerDependencies": {
+        "react": "16.x || 17.x || 18.x || 19.x",
+        "react-dom": "16.x || 17.x || 18.x || 19.x"
+      }
+    },
     "node_modules/react-dom": {
       "version": "19.2.7",
       "resolved": "https://registry.npmjs.org/react-dom/-/react-dom-19.2.7.tgz",
@@ -2598,6 +2843,18 @@
         "react": "^19.2.7"
       }
     },
+    "node_modules/react-is": {
+      "version": "16.13.1",
+      "resolved": "https://registry.npmjs.org/react-is/-/react-is-16.13.1.tgz",
+      "integrity": "sha512-24e6ynE2H+OKt4kqsOvNd8kBpV65zoxbA4BVsEOB3ARVWQki/DHzaUoC5KuON/BiccDaCCTZBuOcfZs70kR8bQ==",
+      "license": "MIT"
+    },
+    "node_modules/react-lifecycles-compat": {
+      "version": "3.0.4",
+      "resolved": "https://registry.npmjs.org/react-lifecycles-compat/-/react-lifecycles-compat-3.0.4.tgz",
+      "integrity": "sha512-fBASbA6LnOU9dOU2eW7aQ8xmYBSXUIWr+UmF9b1efZBazGNO+rcXT/icdKnYm2pTwcRylVUYwW7H1PHfLekVzA==",
+      "license": "MIT"
+    },
     "node_modules/react-router": {
       "version": "7.17.0",
       "resolved": "https://registry.npmjs.org/react-router/-/react-router-7.17.0.tgz",
@@ -2910,6 +3167,16 @@
         "punycode": "^2.1.0"
       }
     },
+    "node_modules/uuid": {
+      "version": "8.3.2",
+      "resolved": "https://registry.npmjs.org/uuid/-/uuid-8.3.2.tgz",
+      "integrity": "sha512-+NYs2QeMWy+GWFOEm9xnn6HCDp0l7QBD7ml8zLUmJ+93Q5NF0NocErnwkTkXVFNiX3/fpC6afS8Dhb/gz7R7eg==",
+      "deprecated": "uuid@10 and below is no longer supported.  For ESM codebases, update to uuid@latest.  For CommonJS codebases, use uuid@11 (but be aware this version will likely be deprecated in 2028).",
+      "license": "MIT",
+      "bin": {
+        "uuid": "dist/bin/uuid"
+      }
+    },
     "node_modules/vite": {
       "version": "8.0.16",
       "resolved": "https://registry.npmjs.org/vite/-/vite-8.0.16.tgz",
@@ -3078,6 +3345,15 @@
         }
       }
     },
+    "node_modules/warning": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/warning/-/warning-3.0.0.tgz",
+      "integrity": "sha512-jMBt6pUrKn5I+OGgtQ4YZLdhIeJmObddh6CsibPxyQ5yPZm1XExSyzC1LCNX7BzhxWgiHmizBWJTHJIjMjTQYQ==",
+      "license": "BSD-3-Clause",
+      "dependencies": {
+        "loose-envify": "^1.0.0"
+      }
+    },
     "node_modules/which": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",
diff --git a/gerbil-manager-web/package.json b/gerbil-manager-web/package.json
index d8e784f..7b59a50 100644
--- a/gerbil-manager-web/package.json
+++ b/gerbil-manager-web/package.json
@@ -13,6 +13,7 @@
   },
   "dependencies": {
     "react": "^19.2.6",
+    "react-d3-tree": "^3.6.6",
     "react-dom": "^19.2.6",
     "react-router-dom": "^7.17.0"
   },
diff --git a/gerbil-manager-web/src/App.tsx b/gerbil-manager-web/src/App.tsx
index 27e4f61..204c7f0 100644
--- a/gerbil-manager-web/src/App.tsx
+++ b/gerbil-manager-web/src/App.tsx
@@ -8,6 +8,7 @@ import GenetikPage from './pages/GenetikPage'
 import HomePage from './pages/HomePage'
 import LittersPage from './pages/LittersPage'
 import NotFoundPage from './pages/NotFoundPage'
+import StammbaumPage from './pages/StammbaumPage'
 
 export default function App() {
   return (
@@ -20,6 +21,7 @@ export default function App() {
             <Route path="neu" element={<GerbilFormPage />} />
             <Route path=":id" element={<GerbilDetailPage />} />
             <Route path=":id/bearbeiten" element={<GerbilFormPage />} />
+            <Route path=":id/stammbaum" element={<StammbaumPage />} />
           </Route>
           <Route path="wuerfe" element={<LittersPage />} />
           <Route path="zuechter" element={<BreedersPage />} />
diff --git a/gerbil-manager-web/src/pages/StammbaumPage.tsx b/gerbil-manager-web/src/pages/StammbaumPage.tsx
new file mode 100644
index 0000000..36046ce
--- /dev/null
+++ b/gerbil-manager-web/src/pages/StammbaumPage.tsx
@@ -0,0 +1,44 @@
+/**
+ * FEAT-4: Stammbaum (Ahnentafel) — interaktiver Stammbaum-Viewer.
+ *
+ * Erster Ausbauschritt: Route + Grundgerüst (Tier laden, Titel, Rücksprung).
+ * Der eigentliche Viewer (react-d3-tree, Druckansicht, Inzuchtkoeffizient)
+ * folgt in den nächsten FEAT-4-Commits.
+ */
+import { Link, useParams } from 'react-router-dom'
+import { de } from '../strings/de'
+import { getGerbil } from '../api/gerbils'
+import { useApi } from '../hooks/useApi'
+
+export default function StammbaumPage() {
+  const t = de.pages.stammbaum
+  const { id = '' } = useParams()
+
+  const gerbil = useApi(() => getGerbil(id), [id])
+
+  if (gerbil.loading) return <p className="muted">{de.common.loading}</p>
+  if (gerbil.error || !gerbil.data) {
+    return (
+      <section className="page">
+        <p className="muted">{gerbil.error ?? t.notFound}</p>
+        <Link to="/rennmaeuse" className="btn">
+          {de.pages.gerbils.detail.back}
+        </Link>
+      </section>
+    )
+  }
+
+  const g = gerbil.data
+  return (
+    <section className="page">
+      <header className="page-head">
+        <h2>{t.titleFor(g.name)}</h2>
+        <div className="head-actions">
+          <Link to={`/rennmaeuse/${g.id}`} className="btn">
+            {t.backToAnimal}
+          </Link>
+        </div>
+      </header>
+    </section>
+  )
+}