Number of mammals up since 1995, protected species decreased after 2011

30/10/2023 15:00

Between 1995 and 2022, Dutch populations of 35 mammal species have increased by approximately 45 percent on average. For example, beavers and otters have increased substantially, spreading again across a large part of the country. In recent years, however, the average increase in these mammals has stalled. Common rabbits, root voles and hazel dormouses, among other species, declined in number or distribution over the past decade. This is evident from new figures released by Statistics Netherlands (CBS), in collaboration with the Dutch Mammal Society.

For most of 35 mammal species, population trends are monitored based on data from monitoring networks of the so-called Network Ecological Monitoring (NEM) (Dutch only). This is a collaboration between the ministries of Agriculture, Nature and Food Quality (LNV) and Infrastructure and Water Management (I&W), the provincial authorities and a few government organisations, including CBS. NEM monitoring focuses primarily on species of The Habitats Directive, as this directive requires both protection and monitoring. Other, easily trackable species are part of the NEM monitoring programmes as well, enabling approximately half of all Dutch (land) mammals to be monitored.

Mammals
	Observation (Index (1995=100))	Trend (Index (1995=100))	Confidence interval (Index (1995=100))
1995	100.85	100	96.1 − 103.65
1996	103.69	99.27	96.26 − 102.16
1997	101.04	99.07	96.73 − 101.25
1998	99.37	99.47	97.66 − 101.32
1999	97.98	100.56	98.99 − 102.15
2000	96.77	102.27	100.82 − 103.8
2001	90.07	104.37	102.89 − 105.95
2002	101.36	107.37	105.81 − 109.06
2003	111.54	111.56	109.97 − 113.32
2004	120.99	116.34	114.66 − 118.34
2005	124.5	121.03	119.23 − 123.08
2006	127.81	126.02	124.31 − 127.9
2007	135.83	131.46	129.65 − 133.34
2008	139.55	136.08	134.28 − 138.04
2009	134.85	139.21	137.42 − 141.1
2010	136.56	141.38	139.59 − 143.21
2011	142.42	142.96	141.18 − 144.86
2012	145.91	144.36	142.44 − 146.35
2013	144.08	145.44	143.63 − 147.36
2014	149.79	146.05	144.32 − 147.76
2015	151.05	146.6	144.97 − 148.23
2016	144.47	147.12	145.57 − 148.74
2017	144.86	147.37	145.99 − 148.87
2018	141.7	147.38	146.02 − 148.77
2019	144.01	147.15	145.71 − 148.63
2020	150.36	146.72	144.95 − 148.48
2021	147.71	146.07	143.84 − 148.32
2022	145.75	145.2	142.3 − 148.15
Source: NEM (Dutch Mammal Society, CBS)

Mammals
	Observation (Index (1995=100))	Trend (Index (1995=100))	Confidence interval (Index (1995=100))
1995	100.85	100	96.1 − 103.65
1996	103.69	99.27	96.26 − 102.16
1997	101.04	99.07	96.73 − 101.25
1998	99.37	99.47	97.66 − 101.32
1999	97.98	100.56	98.99 − 102.15
2000	96.77	102.27	100.82 − 103.8
2001	90.07	104.37	102.89 − 105.95
2002	101.36	107.37	105.81 − 109.06
2003	111.54	111.56	109.97 − 113.32
2004	120.99	116.34	114.66 − 118.34
2005	124.5	121.03	119.23 − 123.08
2006	127.81	126.02	124.31 − 127.9
2007	135.83	131.46	129.65 − 133.34
2008	139.55	136.08	134.28 − 138.04
2009	134.85	139.21	137.42 − 141.1
2010	136.56	141.38	139.59 − 143.21
2011	142.42	142.96	141.18 − 144.86
2012	145.91	144.36	142.44 − 146.35
2013	144.08	145.44	143.63 − 147.36
2014	149.79	146.05	144.32 − 147.76
2015	151.05	146.6	144.97 − 148.23
2016	144.47	147.12	145.57 − 148.74
2017	144.86	147.37	145.99 − 148.87
2018	141.7	147.38	146.02 − 148.77
2019	144.01	147.15	145.71 − 148.63
2020	150.36	146.72	144.95 − 148.48
2021	147.71	146.07	143.84 − 148.32
2022	145.75	145.2	142.3 − 148.15
Source: NEM (Dutch Mammal Society, CBS)

Sharp increase in otters and beavers

Populations of 18 mammal species increased between 1995 and 2022. A sharp increase was seen in particular among five of them: beaver, otter, hamster, bank vole and Natterer's bat. For the beaver and otter populations, this was partly the result of reintroduction in the late 1980s and early 2000s, respectively, and for hamsters of a breeding programme as of 2002. Populations of 12 species, including five mouse species, dropped. The confidence interval of the common vole is unclear due to strong fluctuations, and the remaining four species of bats and mice show stable populations.

Otter and beaver population trends
	Observation otters (Index (2003=100))	Trend otters (Index (2003=100))	Confidence interval otters (Index (2003=100))	Observation beavers (Index (2003=100))	Trend beavers (Index (2003=100))	Confidence interval beavers (Index (2003=100))
1993				60.49	32.41	31.19 − 33.58
1994				25.34	32.65	32.04 − 33.27
1995				25.34	33.62	32.72 − 34.47
1996				25.34	35.47	34 − 37.04
1997				25.34	38.53	36.4 − 40.79
1998				79.76	42.98	40.16 − 46.06
1999				30.71	48.87	45.22 − 52.86
2000				96.96	56.22	51.69 − 61.08
2001				39.76	66.5	61.1 − 72.22
2002				47.56	81.25	74.65 − 88.48
2003	109.53	100	85.22 − 119.22	107.5	100	92.09 − 108.97
2004	92.81	108.61	95.74 − 124.79	223.86	120.93	111.12 − 131.77
2005	128.45	121.43	106.82 − 137.93	132.51	141.61	130.59 − 152.73
2006	132.67	139.82	121.41 − 158.62	223.33	164.31	152.37 − 176.81
2007	156.87	165.92	143.62 − 189.2	215.96	195.01	181.01 − 209.82
2008	261.37	203.92	177.2 − 233.62	273.24	236.85	220.93 − 254.15
2009	286.73	258.14	223.3 − 296.71	133.55	288.67	269.74 − 308.99
2010	216.09	341.12	296.27 − 391.76	219.69	353.65	329.78 − 380.01
2011	451.34	461.49	405.25 − 522.47	505.15	436.2	406.36 − 470.26
2012	781.87	625.21	550.3 − 709.83	709.53	551.65	514.54 − 591.33
2013	873.35	849.92	749.39 − 960.08	899.23	707.46	661.9 − 755.01
2014	1152.16	1130.2	988.64 − 1281.6	1146.29	882.04	826.79 − 939.57
2015	1377.26	1399.92	1230.37 − 1583.56	1288.52	1069.04	1002.72 − 1138.18
2016	1542.07	1616.29	1425.07 − 1816.25	1449.45	1289.88	1214.28 − 1368.89
2017	1795.46	1794.76	1604.75 − 2020.65	1569.06	1539.38	1450.27 − 1628.07
2018	2004.17	1944.05	1741.1 − 2161.74	1750.68	1805.42	1691.55 − 1917.89
2019	1788.16	2031.96	1803.48 − 2266.46	2059.95	2075.57	1929.48 − 2228.21
2020	1925.37	2059.48	1784.44 − 2363.81	2164.79	2347.52	2136.79 − 2561.75
2021	2245.26	2018.6	1638.21 − 2465.94	2517.25	2619.56	2326.29 − 2937.83
Source: NEM (Dutch Mammal Society, CBS)

Otter and beaver population trends
	Observation otters (Index (2003=100))	Trend otters (Index (2003=100))	Confidence interval otters (Index (2003=100))	Observation beavers (Index (2003=100))	Trend beavers (Index (2003=100))	Confidence interval beavers (Index (2003=100))
1993				60.49	32.41	31.19 − 33.58
1994				25.34	32.65	32.04 − 33.27
1995				25.34	33.62	32.72 − 34.47
1996				25.34	35.47	34 − 37.04
1997				25.34	38.53	36.4 − 40.79
1998				79.76	42.98	40.16 − 46.06
1999				30.71	48.87	45.22 − 52.86
2000				96.96	56.22	51.69 − 61.08
2001				39.76	66.5	61.1 − 72.22
2002				47.56	81.25	74.65 − 88.48
2003	109.53	100	85.22 − 119.22	107.5	100	92.09 − 108.97
2004	92.81	108.61	95.74 − 124.79	223.86	120.93	111.12 − 131.77
2005	128.45	121.43	106.82 − 137.93	132.51	141.61	130.59 − 152.73
2006	132.67	139.82	121.41 − 158.62	223.33	164.31	152.37 − 176.81
2007	156.87	165.92	143.62 − 189.2	215.96	195.01	181.01 − 209.82
2008	261.37	203.92	177.2 − 233.62	273.24	236.85	220.93 − 254.15
2009	286.73	258.14	223.3 − 296.71	133.55	288.67	269.74 − 308.99
2010	216.09	341.12	296.27 − 391.76	219.69	353.65	329.78 − 380.01
2011	451.34	461.49	405.25 − 522.47	505.15	436.2	406.36 − 470.26
2012	781.87	625.21	550.3 − 709.83	709.53	551.65	514.54 − 591.33
2013	873.35	849.92	749.39 − 960.08	899.23	707.46	661.9 − 755.01
2014	1152.16	1130.2	988.64 − 1281.6	1146.29	882.04	826.79 − 939.57
2015	1377.26	1399.92	1230.37 − 1583.56	1288.52	1069.04	1002.72 − 1138.18
2016	1542.07	1616.29	1425.07 − 1816.25	1449.45	1289.88	1214.28 − 1368.89
2017	1795.46	1794.76	1604.75 − 2020.65	1569.06	1539.38	1450.27 − 1628.07
2018	2004.17	1944.05	1741.1 − 2161.74	1750.68	1805.42	1691.55 − 1917.89
2019	1788.16	2031.96	1803.48 − 2266.46	2059.95	2075.57	1929.48 − 2228.21
2020	1925.37	2059.48	1784.44 − 2363.81	2164.79	2347.52	2136.79 − 2561.75
2021	2245.26	2018.6	1638.21 − 2465.94	2517.25	2619.56	2326.29 − 2937.83
Source: NEM (Dutch Mammal Society, CBS)

Decline among protected mammals

Over the past 12 years, the average trend of mammals has stabilised, after increasing previously. Eleven species have actually decreased in recent years, either in population or in distribution. This is particularly true for common rabbits. Five declining species are covered by the Habitats Directive: root vole, serotine bat, whiskered bat, brown long-eared bat and hazel dormouse, of which the latter three species were still increasing before 2011. The Netherlands has a special responsibility for root voles, as they are a distinct subspecies that does not exist outside the Netherlands.

Hazel dormouse and root vole population trends
	Observation root vole (Index (1995=100))	Trend root vole (Index (1995=100))	Confidence root vole (Index (1995=100))	Observation hazel dormouse (Index (1995=100))	Trend hazel dormouse (Index (1995=100))	Confidence interval hazel dormouse (Index (1995=100))
1992				255.11	142.85	110.19 − 187.01
1993				142.93	122.99	98.54 − 153.42
1994				75.47	109	90.01 − 130.98
1995	100.82	100	91.33 − 109.36	97.83	100	83.61 − 120.18
1996	91.08	98.06	91.2 − 104.99	97.95	95.34	79.71 − 112.95
1997	101.25	96.41	91.28 − 101.61	47.54	93.99	78.94 − 111
1998	94.94	95.06	91.18 − 99.22	28.86	95.07	80.05 − 112.01
1999	101.52	94.02	90.36 − 97.9	94.24	97.95	83.07 − 115.47
2000	94.23	93.26	89.5 − 96.95	140.23	106.37	91.13 − 123.71
2001	91.94	92.73	88.91 − 96.62	138.69	123	107.36 − 141.03
2002	89.1	92.43	88.43 − 96.45	216.76	144.93	128.74 − 164
2003	85.47	92.38	88.22 − 96.53	132.68	166.49	148.65 − 187.26
2004	91.11	92.56	88.35 − 96.73	244.78	185.02	167.04 − 206.63
2005	94.15	92.95	88.85 − 97.12	181.54	203.07	184.79 − 223.38
2006	89.81	94.16	90.49 − 98.21	194.01	219.94	201.32 − 240.2
2007	106.28	96.02	92.43 − 99.83	357.5	234.85	214.98 − 256.32
2008	98.24	97.3	93.8 − 101.14	184.74	246.85	226.98 − 268.3
2009	95.81	97.74	94.51 − 101.21	253.38	256.1	236.02 − 276.71
2010	101.1	97.92	95.1 − 101.05	228.65	263.63	243.05 − 283.83
2011	95	97.78	95.08 − 100.66	374.25	270.69	249.47 − 291.79
2012	97.97	97.26	94.53 − 100.17	183.2	278.13	257 − 299.49
2013	96.04	96.37	93.7 − 99.03	234.16	284.54	263.4 − 305.5
2014	95.5	95.2	92.47 − 97.83	398.36	287.85	267.49 − 308.54
2015	91.92	93.8	91.03 − 96.47	345.29	285.95	266.44 − 305.95
2016	91.23	92.17	89.55 − 94.73	341.91	279.43	261.01 − 299.05
2017	92.1	90.3	87.47 − 92.83	209.25	270.02	253.35 − 288.59
2018	91.02	88.21	85.03 − 91.17	278.06	257.61	242.27 − 274.73
2019	80	85.91	81.93 − 89.66	239.96	242.26	225.74 − 260.09
2020	88.2	83.43	78.32 − 88.62	262.76	224.35	205.66 − 243.73
2021	82.5	80.78	74.41 − 87.45	214.88	204.78	184.12 − 226.97
2022	75.61	77.98	70.28 − 86.52	153.67	184.44	162.38 − 210.49
Source: NEM (Dutch Mammal Society, CBS)

Hazel dormouse and root vole population trends
	Observation root vole (Index (1995=100))	Trend root vole (Index (1995=100))	Confidence root vole (Index (1995=100))	Observation hazel dormouse (Index (1995=100))	Trend hazel dormouse (Index (1995=100))	Confidence interval hazel dormouse (Index (1995=100))
1992				255.11	142.85	110.19 − 187.01
1993				142.93	122.99	98.54 − 153.42
1994				75.47	109	90.01 − 130.98
1995	100.82	100	91.33 − 109.36	97.83	100	83.61 − 120.18
1996	91.08	98.06	91.2 − 104.99	97.95	95.34	79.71 − 112.95
1997	101.25	96.41	91.28 − 101.61	47.54	93.99	78.94 − 111
1998	94.94	95.06	91.18 − 99.22	28.86	95.07	80.05 − 112.01
1999	101.52	94.02	90.36 − 97.9	94.24	97.95	83.07 − 115.47
2000	94.23	93.26	89.5 − 96.95	140.23	106.37	91.13 − 123.71
2001	91.94	92.73	88.91 − 96.62	138.69	123	107.36 − 141.03
2002	89.1	92.43	88.43 − 96.45	216.76	144.93	128.74 − 164
2003	85.47	92.38	88.22 − 96.53	132.68	166.49	148.65 − 187.26
2004	91.11	92.56	88.35 − 96.73	244.78	185.02	167.04 − 206.63
2005	94.15	92.95	88.85 − 97.12	181.54	203.07	184.79 − 223.38
2006	89.81	94.16	90.49 − 98.21	194.01	219.94	201.32 − 240.2
2007	106.28	96.02	92.43 − 99.83	357.5	234.85	214.98 − 256.32
2008	98.24	97.3	93.8 − 101.14	184.74	246.85	226.98 − 268.3
2009	95.81	97.74	94.51 − 101.21	253.38	256.1	236.02 − 276.71
2010	101.1	97.92	95.1 − 101.05	228.65	263.63	243.05 − 283.83
2011	95	97.78	95.08 − 100.66	374.25	270.69	249.47 − 291.79
2012	97.97	97.26	94.53 − 100.17	183.2	278.13	257 − 299.49
2013	96.04	96.37	93.7 − 99.03	234.16	284.54	263.4 − 305.5
2014	95.5	95.2	92.47 − 97.83	398.36	287.85	267.49 − 308.54
2015	91.92	93.8	91.03 − 96.47	345.29	285.95	266.44 − 305.95
2016	91.23	92.17	89.55 − 94.73	341.91	279.43	261.01 − 299.05
2017	92.1	90.3	87.47 − 92.83	209.25	270.02	253.35 − 288.59
2018	91.02	88.21	85.03 − 91.17	278.06	257.61	242.27 − 274.73
2019	80	85.91	81.93 − 89.66	239.96	242.26	225.74 − 260.09
2020	88.2	83.43	78.32 − 88.62	262.76	224.35	205.66 − 243.73
2021	82.5	80.78	74.41 − 87.45	214.88	204.78	184.12 − 226.97
2022	75.61	77.98	70.28 − 86.52	153.67	184.44	162.38 − 210.49
Source: NEM (Dutch Mammal Society, CBS)

Sources

Website - Environmental Data Compendium - Trend fauna